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.
Death Egg
While in the Death Egg, defeat the big robot, and enable the "Super Sonic", "Debug" and "Level select" codes. Start running out of the Death Egg. While running out, turn into an object, then back to Sonic. Go back to the robot room, and another robot will be there. The explosions that follow you out will follow you while you fight the robot. You can go back a few times using this technique.
Death Egg Zone: Rings
Enable the "Level select" and "Debug" codes. Go to the Death Egg zone, turn your self into a ring, and press C to multiply yourself. Then, turn back into Sonic and collect the rings. This should keep you from dying for awhile.
Debug Mode
Go to the option menu when at the title screen. Using the sound test play 01,09,09,02,01,01,02,04 in that order to activate Debug Mode. If you entered it correctly you'll here a ring chime. Then depending on your controller, press Start or + to go back to the title screen. On the Wii remote press A + Start or on the Gamecube controller press B + Start to start the game using debug mode otherwise it will start without it activated.
Emerald Hill music
To hear the Emerald Hill melody at the title screen, go to sound test selection in the options menu and listen to songs 1, 1, 2 and 4 in order. Then, highlight "Player Select" and press Start. You will hear the Oil Ocean music at the beginning of the first level. Reset the game, and you will hear the Emerald Hill music.
Extra lives
Enable the "Debug mode" code and start a game with Sonic and Tails. Press Down + Jump (Spin Dash) then press B to turn into an object. Turn into an enemy and place him on Tails. He will still be Spin Dashing. Your points will soon double and you will get lives every second, or depending how fast, you place the enemy by pressing C. Once you have enough lives, turn back into Sonic by pressing B again. This is much faster than setting the alarm off in Launch Base Zone. Note: This works with any other Sonic game that has debug mode. More compact enemies work better than the larger ones. For example, in Aquatic Ruin, the Fly is much more efficient than the Grounders.
Faster sound test options
Go into the options screen, bring up the sound test, then press A. You will go up ten at a time, making it much easier when using the level select code.
Fiery Defeat in Death Egg
Enable the "Debug mode" code and make sure you can be Super Sonic. Gain enough rings so that you will be Super Sonic for quite some time. Defeat Metal Sonic and chase Robotnik and defeat him. When the Death Egg is exploding, and you are running down the shaft to exit, enter debug mode. Change back and run back inside. Robotnik will return and you can defeat him again, however you will be surrounded by fire. When you defeat him again, you will have twice the amount of fire behind when you run out. Note: when this is going on the game will be very slow and you will not actually see Sonic -- make sure you are still Super Sonic when executing this trick.
Mega Sonic
Collect fifty rings and jump after becoming Hyper Sonic for even more speed and higher jumps.
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.
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.
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.
Use Tails as a key
Use the following trick if you are stuck or just want a huge shortcut. Play an adventure with Sonic and Tails. Whenever you find a one-way door (a door that will open from one way but not for the other), walk in the opposite direction of it so that it is just off-screen. The game will not detect the door because it is not on-screen. Make Tails go past the door off-screen with controller two. Then with controller one, move closer to the locked door. It should be open and you should be able to get past it. This could cut off up to three quarters off a long level.