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 regular Sonic.
Enable the "Level select", "Debug" and "All Chaos Emeralds" 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 doesn't affect 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; so 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.
First, enable the "Debug mode" code. During game play, press the button configured as "B" on the Genesis and Sonic should become an object somewhere on the level. Press the button configured as "C" to"paste" that object in the level. To resume game play, the button configured as "B". To change the object, press the button configured as "A" on the Genesis while editing the level. You can also move the object in the air, etc. to truly make your own areas. You can also move across obstacles and turn back to Sonic to cut points in the level.
In two player vs. mode, hit as many item boxes as possible until you get the speed shoes. Then, 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 should still have the speed shoes in effect for the rest of the stage.
After completing a level, run off screen and wait for the end-of-level sign shows Sonic. When it does, transform into Super Sonic and the sign will show Super Sonic for one second, then show blue Sonic again.
Enable the "All emeralds", "Level select", and "Debug mode" codes, then go to Oil Ocean (either act). Become Super Sonic and stand on one of the green/yellow colored cylinders. Jump on it and as soon as you hear it break, go into debug mode. You should be thrust upward, even in your debug state. As soon as you regain traction, exit debug mode to be able to jump twice as high and fast.
In Wing Fortress, collect some rings and move as far to the right as possible without climbing. When blades try to block your way, hit them. As soon as you are invincible, walk through them, then ump on the platforms to the right and half the level will be completed.
To receive 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. Complete a zone in the following times to earn the corresponding points:
Enable the "Level select" and "Debug mode" codes, then go to Emerald Hill Zone Act 1 or 2. Transform into the default ring and press SQUARE(4) to become an invisible object. You will be a waterfall. Place waterfalls by repeatedly pressing A from where you start to over by the "coconuts" enemy in the tree . Eventually you will see the life counter in the corner change to Ashura's. Turn Sonic into himself again and he should come out as Ashura, a green and black version of Sonic. You can change his color by continuing to place waterfalls. Watch the life monitor to see the changes in color.
Enable the "Level select" code and select the sound test selection on the options screen. Choose sounds 4, 1, 2, 6 (in that order), start a stage, then collect 50 rings. Jump to transform into Super Sonic.
Enable the "Level select", "Super Sonic", and "Debug mode". On any stage, get fifty rings and turn into Super Sonic. Change Sonic into the television monitor, then 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, which will be destroyed because Tails is invincible. You will get tons of points, which add up to extra lives.
Enable the "Debug mode" code, as well as the "Super Sonic" code if desired. Go to Death Egg Zone and 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, then go back to where you battled the egg robot. Flames should follow Sonic where ever he goes.