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.
Play this sequence at the level select sound test screen:
1, 9, 9, 2, 1, 1, 2, 4. Then, hold A + Start as you enter a level.
Play in the dark:
Hold C + Start at the level select menu.
Play this sequence at the level select sound test screen: 4, 1, 2, 6.
Select any level, get 50 rings, then jump.
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.