Sonic the Hedgehog 2/Cheats

Stage Select
In the options screen play music 19, 65, 09, 17, then press Start. This should return you to the title screen. Hold A and press Start again and a level select menu should appear.

Receive All Chaos Emeralds
In the level select screen, play music 04, 01, 02, 06. 06 will be the sound heard when you receive a Chaos Emerald instead of what it normally is, if the cheat was done properly. Now you may go to any level. To turn into Super Sonic, collect fifty (50) rings and then jump.