Level Select-Go to the Angel Island Zone or the Mushroom Hill Zone. If you go to Angel Island, jump on one of the vines. If you go to the Mushroom Hill, jump on one of the pull up machines. Press Up, Up, Up, Left, Left, Left, Right, Right, Right. If you hear a special tone, (it's the noise you hear when you get a ring) you did it right. Press Start and then press A. It should restart the Sega. At the title screen, go down to Competition and then down again. Sound Test is there.
Debug-C-Do Level Select in both Angel Island and Mushroom Hill. Then, go to Level select and choose the level you want. Press A and hold it and press Start to go to a level in debug. Use A to change between items while you are debugged, B to change from Sonic to Debug, and C to lay an item. If you press A while you are Sonic, Gravity will change like in the Death Egg 2.
Get Extra points in Hidden Palace (Sonic's version)-S-Do Debug and then go to Hidden Palace (Sonic's version). Go forward till you are all the way up the steps, then you should see someplace you can go up if you didn't have limited flying. You should find a fire shield, water shield, lightning shield, 2 ring PC's, an extra life PC, and a star PC.
Easy Emeralds-C-To gain all the chaos emeralds, enter the Level Select code, then highlight "Special Stage" and press C + Start. After receiving the emerald, press A + Start and repeat the process until you have them all.
Alternatively, enter the Sound Test code and play sounds 2, 4, 5, 6 in order. If you did it correctly, the Emerald sound will play.