Sega Genesis Collection Cheats
Hold Square, push start repeatedly
Enable Options, choose a level, and press Start while holding Square
On the title screen, hold X and push Start
On the title screen, hold Square, X, Circle, Down, Left, and Start
On the title screen, hold Square, Circle, Up/Right, and Start
Sonic the Hedgehog
At the title screen, press Up, Down, Left, Right, and press start while holding X.