Sonic The Hedgehog 2
To unlock the level selection screen, at the sound test selection on the options menu, choose sounds 19, 65, 9, and 17 (in that order). Hold Circle and press Start. Hold Square and press Start when Sonic and Tails appear at the title screen.
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). Select any starting level, then hold Square + 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.
Enable the "Debug mode" code. During a game, press the button configured as "B" on the Genesis. Sonic should become an object somewhere on the level. Press the button configured as "C". You can "paste" that object in the level. Press the button configured as "B" again to resume the game. Press the button configured as "A" on the Genesis while editing the level to change the object. You can also move the object in the air, etc. to truly make your own challenge. Also, you can move across obstacles and turn back to Sonic to cut points in the level.
To unlock Super Sonic, at the title screen, press Up and access the "Options" screen. Go to "Sound Select" and listen to sounds 19, 65, 9, 17 (in that order.). Hold Circle + Start to return to the title screen. Hold Square + Start to go to the level select menu. Go to the new sound select and listen to sounds 1, 9, 9, 2, 1, 1, 2, 4 (in that order). Now, listen to sounds 4, 1, 2, 6 (in that order). You should hear the Emerald sound effect. Highlight your level, then hold Square + Start. Keep the buttons held until game play begins. Turn into a ring, appear overlapped with Tails, and keep spawning rings directly where he is standing. When you have set 50 rings into him, turn back to normal and jump to become Super Sonic.
Enable the "Level select" code. Use the sound test selection on the options screen. Choose sounds 4, 1, 2, 6 (in that order). Start a stage, collect 50 rings, then jump to transform into Super Sonic.
To begin the game with fourteen continues, at the sound test menu, choose sounds 01, 01, 02 and 04 (in that order), then press Start.
Tails name changed to Miles:
To change "Tails" to "Miles", at the title screen, press Up(3), Down(3), Up. Note: The opposite will occur in the Japanese version of the game.
Press Start and hold X. Use Circle to jump and there will be no music. Your time will now stay at 0:00.
Super Tails and Super Sonic:
Enable the "Level select" and "Debug mode" codes. Then, start any level and get 50 rings. You can use the "Turn into a ring and give them to Tails" trick. When you turn into Super Sonic, use debug mode to turn into a television. It should be a "switch" television from versus mode when you place it. If you break it, you will see a brief glitch, which will not effect the game. You will see everything return, with one small difference. You will still have Super Sonic's appearance, but he plays like Sonic with regular speed, normal jumps, etc. Tails, however, has Super Sonic's power and cannot be "hurt". This will last for however many rings you had when you hit the television; start when you have at least 100 rings. Then, hurt yourself so that you lose all your rings and you will lose Super Sonic's appearance. Then, use the trick to get fifty rings again and jump. You should now have Super Sonic and Super Tails.
Collect fifty rings and jump after becoming Hyper Sonic for even more speed and higher jumps.
Enable the "Level select" and "Debug mode" codes. Then, go to Emerald Hill Zone Act 1 or 2. Transform into the default ring, then press Square(4) to become an invisible object. You will be a waterfall. Place waterfalls by constantly pressing A from where you start to over by the "coconuts" enemy in the tree . You will eventually see the life counter in the corner change to Ashura's. Turn Sonic into himself again and he should come out as Ashura, his brother. You can change his color by continuing to place waterfalls; if you watch the life monitor, you will see the changes in color.
Enable the "Level select", "Play as Super Sonic", and "Debug mode" codes and enter any stage. Get fifty rings and turn into Super Sonic. Change Sonic into the television monitor. Change Sonic back and have him jump to turn into Super Sonic. Jump on the television monitor to have Tails become invincible. Then, turn into an enemy and put it right on tails while he is invincible. Continuously place the robots there, and they will be destroyed because Tails is invincible. You should get lots of points, which adds up to extra lives.
Infinite speed shoes:
Begin a game 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.
Super Sonic sign:
Get all of the Chaos Emeralds and transform into Super Sonic. Try to have at least fifty rings when you finish the level. After completing the level, run off screen and wait until the end-of-level sign shows Sonic. When it does, transform into Super Sonic. The sign will show Super Sonic for one second, then show blue Sonic again.
Starry Super Sonic:
Get all the Chaos Emeralds and collect fifty rings, but do not transform into Super Sonic yet. Find an invincibility monitor and spin (do not jump) into it. Then, transform into Super Sonic. If done correctly, the stars will surround Super Sonic until he runs out of rings and transforms back into blue Sonic. Note: This does not improve Super Sonic's performance.
Stronger Super Sonic:
Enable the "Level select" and "Debug mode" codes. Go to Oil Ocean (either act). Become Super Sonic, then stand on one of the green/yellow colored cylinders. Jump on it, but as soon as you hear it break, go into debug mode. You should be thrust upward, even in your debug state. Then as soon as you regain traction, exit debug mode. You should now be able to jump twice as high and fast.
Flames follow Sonic:
Enable the "Debug mode" code. You can also enable the "Play as Super Sonic" code, if desired. Go to Death Egg Zone and defeat the two bosses. When you defeat the giant egg robot, turn into a ring instead of running all the way out. Go into the area where flames appear. Go back to where you battled the egg robot. Flames should follow you where ever you go.
Wing Fortress shortcut:
In Wing Fortress, move with some rings as far to the right as possible without climbing. When blades appear to block your way, hit them. As soon as you are invincible, walk through them. Jump on the platforms to the right and half the level will be completed.
For extra points, pass any zone in a certain amount of time. For the best bonus, enter the "Debug mode" code. The clock will stop and you will always score a 50,000 bonus.
0:30 - 50,000
0:45 - 10,000
1:00 - 5,000
1:30 - 4,000
2:00 - 3,000
3:00 - 2,000
4:00 - 1,000
5:00 - 500