Use the sound test selection on the options menu. Choose sounds 19, 65, 9, and 17 (in that order) and press [C] after each selection. A chime will confirm correct code entry. Press [Start]. Hold [A] and press [Start] when Sonic and Tails appear at the title screen.
This trick requires the "Level select" and "Debug mode" codes. Go to any stage and change into an object. Press [A] until you get to the object before the single ring. It is a strange looking object with a little Robotnik head (a machine where all the creatures appear from if you defeated a Boss). Place about ten in a row. Step on the first one until you see the score counting as if you completed the level. When you see that, step on the other buttons. You will go to the level after the level you were supposed to go to. For example: if you were in the Emerald Hill Act 1 you will now be in Chemical Plant Act 1. You can do this trick in any stage, but not in Dead Zone.
Enable the "Debug mode" code and choose any level except the Death Egg. Press [C] to cycle through the sprites until you see a glitched-looking prison egg. Return to Sonic again and get him to step on it. The "Sonic got through Act 1/2" message should appear. This will take you to the next level, and even works on Bosses.
Toggle Tails or Miles
Press [Up]x3, [Down]x3, [Up] at the title screen. A sound will confirm correct code entry. Alternately, press [Up]x2, [Down]x2, [Up]x4.
Super Sonic and Tails
Enable the "Level select" code. Use the sound test selection on the options screen. Choose sounds 4, 1, 2 and 6 (in that order) and press [C] after each selection. Music will confirm correct code entry. Select any starting level and collect 50 rings. Sonic or Tails will turn yellow and can run at super speed, jump twice as far, and become invincible to enemies and spikes. The total number of rings will decrease during super mode. Your character will revert to normal when the ring total reaches zero. Note: Super Sonic or Tails can still drown, be crushed, and fall into bottomless pits.
Alternatively, enable the "Level select" code. Then, press [Start] and hold [A]. Press [Start] when the title screen appears. Then, play songs 1, 9, 9, 2, 1, 1, 2, 4 to activate debug mode. Then play 3, 4, 1, 2, 6. Create 50 rings in debug mode. Jump, make a item box as Super Sonic, and jump on it. Get hit and change back into Super Sonic.
Enable the "Debug mode" code. Create and position a "Transfer Box" monitor. Hit it while as Super Sonic. You lose all your powers but stay yellow. Tails looks the same but has invincibility, with little stars flashing around him. To regain Super Sonic, allow yourself to get hit, then press [B] to turn into a ring and place at least 50 rings on Tails. Press [B] to exit debug mode and jump to become Super Sonic with Super Tails as a follower.
Super Sonic in Death Egg zone
Enable the "Level select", "Debug", and "Super Sonic" codes. Go to the Death Egg zone and turn yourself into a ring. Multiply yourself until there are 50 or more rings. Collect them and jump to become Super Sonic.
Super Sonic animation
To play the Super Sonic animation repeatedly, enable the "Level Select" code, the "Debug Mode" code, followed by the "Super Sonic" code. Go to any level, and any Act (except the single Act levels -- Death Egg, Sky Chase). Complete the Act with more than 50 rings. As the score begins to add up, press [B], turn into an item, then press [B] again. Sonic will do the animation for turning Super Sonic and then return to normal. Press [B] followed by [B] again and he will do the same thing. You can continue to do this as long as the score continues to add up.
Enable the "Super Sonic animation: trick" and pause when Sonic starts to do the animation. If done correctly, he should be white, If not, hold [B] to enter slow motion until he turns white.
Run forward in Oil Ocean, Act 2 until reaching the green jet springs. Jump on the very last spring and hold [Right]. Sonic will hit a group of spikes before becoming stuck in the side of the wall. Jump out to transform into Hyper Sonic. In this mode, Sonic can run faster and jump farther than Super Sonic, but is not invincible.
Collect fifty rings and jump after becoming Hyper Sonic for even more speed and higher jumps.
Enable the "Level select" code. Use the sound test selection on the options screen. Choose sounds 1, 9, 9, 2, 1, 1, 2, 4 (in that order) and press [C] after each selection. A chime will confirm correct code entry. Select any starting level, then hold [A] + [Start] until game play begins. Screen coordinates will appear instead of a score and the number of objects displayed will appear instead of the time remaining. Use one of the following controller actions to enable the corresponding debug code. Note: This code may only be enabled when playing as Tails alone.
Object transformation Continuous music
Press [B] during game play to change Sonic into a game object. Press [A] to change into a new object. Press [C] to place an object on the screen. Press [B] again to revert back to Sonic. Note: The type of object that may be selectable will vary from level to level.
Sonic is, by default, invincible in debug mode.
Pause game play and hold [B].
Pause game play and press [A].
Pause game play and press [C].
Hold [C] and press [Start] when selecting a level.
Place a transfer box monitor on the screen. Hit the monitor as Super Sonic.
Select "Options" at the title screen. At the sound test screen, select each of the following sounds in order and press [C] after each selection: 1, 9, 9, 2, 1, 1, 2, 4. The music from the Oil Ocean zone will play during the entire game.
No music or sound effects
Select 7F at the sound test ascreen and you will not hear any music or sound effects. To return to normal, reset the Genesis.
Easy Chaos Emeralds
Start the game as usual. Get a Chaos Emerald, reset the game, and start the game from the options menu. You will keep the Emeralds that you have gained so far each time you start from the options menu.
Begin the game with either or both character(s). Collect 50 or more rings and go to the first checkpoint you can find (floating on an island in the air near the Speed Shoes by the tops of the waterfalls). Complete the Chaos Emerald stage, getting (or not getting) the first Emerald. Wait until you can see Sonic standing, then reset the game. On the start screen, press [Down]x2 to "Options", and select it. Then press [Right]x2, re-selecting the same character, and press [A]. Gain 50 rings and go to the same checkpoint. You will be on the next Chaos Emerald stage. Continue to do this until you have all the Chaos Emeralds. If you fail on one, just follow the same procedure to redo that stage.
Unlimited speed shoes
Begin game play in two player vs. mode and hit as many item boxes as possible until you get the speed shoes. Then, intentionally lose your life while you have them (getting squashed is the easiest way). You will return to the start of the level or the last Star Post that you hit, but you will now have the speed shoes in effect for the rest of the stage.