Debug Mode:
On the title screen press C, C, Up, Down, Left, Right, then hold A and press Start.

Debug Mode Instructions: B - toggles between normal gameplay and item placement; A - cycle through items; C - place item in level; A+C - cycle backwards through items. And when paused: A - reset game; B - hold for slow motion; C - frame advance.

Alternative Ending Sequence:
Immediately after beating Robotnik in Final Zone, hold A, B and C. Sonic will behave differently during the credits.

View Staff Names on "Sonic Team Presents" Screen (JAP Machine Only):
On the title screen press C, C, C, C, C, C, Up, Down, Left, Right, then hold A, B, C and Down when demo starts.
Screenshot

View Endings (JAP Machine Only):
First perform the Staff Names cheat then the Level Select cheat. Then play sound 9E for the credits or sound 9F for the ending sequence & credits.

Level Select (PAL/US Machine Only):
On the title screen press Up, Down, Left, Right, then hold A and press Start.
Screenshot

Debug Mode (JAP Machine Only):
On the title screen press C, C, C, C, Up, Down, Down, Down, Left, Right, then hold A and press Start.

Debug Mode (PAL/US Machine Only):
On the title screen press C, C, Up, Down, Left, Right, then hold A and press Start.

View Staff Names on "Sonic Team Presents" Screen (JAP Machine Only):
On the title screen press C, C, C, C, C, C, Up, Down, Down, Down, Left, Right, then hold A, B, C and Down when demo starts.
Screenshot

View Endings (JAP Machine Only):
First perform the Staff Names cheat then the Level Select cheat. Then play sound 9E for the credits or sound 9F for the ending sequence & credits.

Debug Mode:
On the title screen press C, C, Up, Down, Down, Down, Down, Up. Then hold A and press Start. Once you're on the level select screen, hold A and press Start to begin a Zone in debug mode.

Debug Mode Instructions: B - toggles between normal gameplay and item placement; A - cycle through items; C - place item in level; A+C - cycle backwards through items. And when paused: A - reset game; B - hold for slow motion; C - frame advance.

2-Player Mode On Any Level:
On the level select screen press B and Start to play a level in 2-player mode. This works on most levels. Some levels work badly and some don't work at all.
Screenshot

Night Mode:
On the level select screen press C and Start to play a level during the night. This works on most levels.
Screenshot

Debug Mode:
On the level select screen, play sounds 01, 09, 09, 02, 01, 01, 02 and 04. Then hold A and press Start to begin a level in debug mode.

Debug Mode Instructions: B - toggles between normal gameplay and item placement; A - cycle through items; C - place item in level; A+C - cycle backwards through items. And when paused: A - reset game; B - hold for slow motion; C - frame advance.

Night Mode:
On the level select screen press C and Start to play a level during the night.

Enable Super Sonic:
On the level select screen play sounds 04, 01, 02 and 06. Select a level, collect 50 rings and jump to become Super Sonic.
Screenshot

Start With 14 Continues:
On the options screen (not the level select screen) play sounds 19, 65, 09, 17, 01, 01, 02 and 04. Highlight "Player Select" and press Start. You'll begin playing Emerald Hill Zone with the wrong music and 14 continues.
Screenshot

Japanese Mode (PAL/US Machine Only):
On the title screen press Up, Up, Up, Down, Down, Down, Up. You'll hear a chime and the game will be set to Japanese mode, meaning Tails is now called Miles and there is no "TM" on the Sega intro screen.
Screenshot

European/American Mode (JAP Machine Only):
Same as the Japanese Mode code. Changes Miles to Tails and adds "TM" to the Sega screen.

Super Tails:
First, enable debug mode and Super Sonic. Next, become Super Sonic. Now create a monitor and break it open. Tails will become "super", and although Sonic still looks "super", he has lost his Super Sonic attributes. To fix this, lose your rings and collect another 50 to become Super Sonic again.
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Hyper Sonic:
Enable debug mode and Super Sonic. Then become Super Sonic, create two monitors next to each other and smash them both with a dash-attack. Sonic will now have stars around him, just like Hyper Sonic from Sonic 3 & Knuckles.
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Finish An Act Wherever You Want:
Enable debug mode. Cycle through the objects by pressing A until you find something that looks like a Prison Egg, albeit with garbled graphics. Create one and jump on top of it. You'll finish the Act without finishing it. This works on every level except Death Egg Zone.
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Two Biplanes On Sky Chase Zone:
Enable debug mode. Create a monitor and smash it. There are now two Tailses, which is interesting, but not even slightly useful.
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Fast-Moving, High-Jumping Sonic:
Enable debug mode and go to Oil Ocean Zone. Create one of those "zoom blocks" (see screenshot) and smash it. As you start to fly away, press B and slow yourself down then press B again. Sonic will now move much more quickly and jump twice as high. For an even better effect, use Super Sonic with this trick.
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Play As Ashura:
Enable debug mode and start playing on Emerald Hill Zone. Without moving away from where you start the level, press B, then keep pressing A until you turn into a vertical line of four rings. Press A once more and you'll turn into an invisible object. Now press C repeatedly (50 or more times) to produce waterfalls. When you've made enough waterfalls, press B to turn back into Sonic and jump out of the waterfall. You should now be playing as Ashura.
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Fight Silver Sonic And The Final Boss Simultaneously:
Enable debug mode and start playing in Death Egg Zone. When you start to fight Silver Sonic, create a monitor and smash it. Immediately press B to stop yourself from dying. You can now move around the Zone freely, which means you can lure the final boss to where Silver Sonic is, and fight them both at the same time.
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Debug Mode:
On the level select screen, simply press A and Start to play a level with debug mode.

Debug Mode Instructions: B - toggles between normal gameplay and item placement; A - cycle through items; C - place item in level; A+C - cycle backwards through items; C+B - displays all Sonic's sprites. And when paused: A - reset game; B - hold for slow motion; C - frame advance.

Instant Super Sonic:
Enter the level select cheat, then use debug mode on any level. To become Super Sonic, create an 'S' monitor and smash it. You will immediately gain 50 rings and turn into Super Sonic.

Start With All 7 Chaos Emeralds:
On the level select screen, play sounds 02, 04, 05 and 06. This also allows you to become Super Sonic.

Special Stage Select:
On the level select screen, play sounds 00, 01, 02, 03, 04, 05 or 06. Then highlight Special Stage Act 2 and press A and Start. Each of the sounds 00 - 06 correspond to the seven Special Stages.

Hidden Special Stage:
On the level select screen, play sound 07. Then highlight Special Stage Act 2 and press A and Start.
Screenshot

Play "Get Blue Spheres" Special Stages:
Lock on Sonic 1 and hold down A+B+C.

Character Selection: The number beneath "Angel Island" represents which character you're playing as. Press C to change it. 00 - Sonic and Tails; 01 - Sonic alone; 02 - Tails; 03 - Knuckles.

Debug Mode:
Enter the level select cheat. Start playing on Mushroom Hill Zone by pressing A and Start. Hang onto one of those lifting machines and press Left, Left, Left, Right, Right, Right, Up, Up, Up, then pause and press A to reset the game. On the title screen go to Sound Test again. Hold A and press Start to play a level with debug mode. Unlike in previous games, the score is still there even though debug mode is on.

Debug Mode Instructions: B - toggles between normal gameplay and item placement; A - cycle through items (reverse gravity in normal gameplay); C - place item in level; A+C - cycle backwards through items; C+B - displays all Sonic's sprites. And when paused: A - reset game; B - hold for slow motion; C - frame advance.

Debug Mode:
On the level select screen, play sounds 01, 09, 09, 04, 01, 00, 01 and 08 then hold A and press Start to begin a level with debug mode.

Debug Mode Instructions: B - toggles between normal gameplay and item placement; A - cycle through items; C - place item in level; A+C - cycle backwards through items. And when paused: A - reset game; B - hold for slow motion; C - frame advance.

All Emeralds:
On the level select screen, play sounds 01, 06, 07, 07, 07, 02, 01 and 06.

Hold A and press Start to go to Lava Powerhouse
Hold B and press Start to go to The Machine
Hold C and press Start to go to Showdown

Level Skip:
Enter the level select cheat, then while playing the game, press Start and A to skip zones.

Debug Mode:
Press Start on Joypad 2 while playing the game.

Debug Mode:
Press Start on Joypad 2 while playing the game.

Sound Effects Test:
Press Start on Joypad 1, and when you see NEW GAME or CONTINUE press A on Joypad 2.

Sound Test:
On the title screen, press Down, Down, Down, Left, Right and A.
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Debug Mode and Hidden Tails Artwork:
On the sound test screen, select sounds FM40, PCM12, and DA11. Press Start to begin a new game in debug mode.
Screenshot

Debug Mode Instructions: B - toggles between normal gameplay and item placement; A - cycle through items; C - place item in level; A+C - cycle backwards through items. And when paused: A - reset game; B - hold for slow motion; C - frame advance.

D.A. Garden:
Complete every level in Time Attack mode in less than 37 minutes in total. Go back to the title screen to find a new option. D.A. Garden is a picture of the Little Planet, which you can scale, rotate and switch between present, good future and bad future. Tails and Metal Sonic will occasionally fly past.

Special Stage In Time Attack:
Complete every level in Time Attack in under 30 minutes in total. You'll now be able to play on the Special Stage in Time Attack mode.

Visual Mode:
Complete Time Attack in under 25 minutes.

View Programmer's best times:
On the title screen, press Right, Right, Up, Up, Down and C.
Screenshot

Cloud Manipulation:
On the title screen, hold A and press Up, Down, Down, Down, Down, Up, then use Joypad 2 to manipulate the clouds.

Hidden Artwork:
On the sound test screen, select sounds:

FM42, PCM04, and DA21 to see Human Sonic ~ Screenshot
FM44, PCM11, and DA09 to see Glassy-eyed Sonic sitting down ~ Screenshot
FM42, PCM03, and DA01 to see MC Sonic ~ Screenshot
FM46, PCM12, and DA25 to see Weird-faced Sonics ~ Screenshot

Hidden Special Stage:
On the sound test screen, select sounds FM07, PCM07, and DA07.
Screenshot

Dancing Amy in the Sound Test:
Go to the colour test screen, enter <00><00><00>, <06><0B><11> and <00><08><17>. Press Start to return to the title screen and then to the sound test menu where a dancing Amy Rose will appear.
Screenshot

Play as Hidden Character:
On the level select menu, choose the character marked ******** and start playing on any level.
Screenshot

Level Select (Master System Version):
When the Sega logo appears, hold Diagonal Up + Left and both Buttons on Pad 2. Keep them held until the title screen appears, then press Button 2 on Pad 1.

Level Select (Master System Version):
At the title screen, press Up, Up, Down, Down, Left, Right, Left, Right, then press button 1.

Anti-Gravity Sonic:
On the options screen, play sounds 0, 9, 0, 1, 6 and 8. To activate hold 1 + 2 + Start.

Skip to the Boss:
On the options screen, play sounds 0, 2, 1, 5, 6 and 6. To activate, press 1 + 2 + Start.

Fast Music:
On the options screen, play sounds 0, 4, 2, 5, 5 and 7.

Bonus Stage:
Go to Zone 2-3. Find the cannon and get into it, then press 1 + 2 + Right. Turn the switch ON to open the bonus door.

Clean Pause:
Pause the game, then press X + Y + Z to remove the menu thing.

Unlock All Levels in Time Attack mode:
To unlock all the levels in Time Attack mode for any of the four games, enter the level select code for that game and play the final level. This will automatically unlock all the levels.

View All Movies Continuously:
In the Movie Theatre, hold X + Y + Z and press A.

A - Skip to next Act
B - Skip to next Zone
C - Skip to the final boss
X - Gain 1 life
Y - Gain 1 medal (10 medals = 1 continue)
Z - Gain all Chaos Emeralds

Change Views in Special Stage:
When you're about to get a Chaos Emerald, press X to "freeze" the view. To view the Emerald from below, hold Z as you approach it.

Clean Pause:
Pause the game, then press X + Y + Z.

Both Players Use The Same Character:
First Player 1 selects their character, then Player 2 selects the same character by pressing X + Y + Z.

Take a Screenshot:
To take a picture in this game of the screen, at any time press F9. Screenshots will be saved into the main S3K folder. They will be named ''Cap00000'', ''Cap00001'' etc, as many as you took.

Sound Test:
On the title screen, press Down, Down, Down, Left, Right and Space.

See The Programmers' High Scores:
On the title screen, press Right, Right, Up, Up, Down and Space.

Debug Mode, Hidden Artwork and Hidden Special Stage:
Same as in Mega CD version.