Git on the rope in STAGE 1 ZONE 1 and do this code in order:

3 Right
3 Left
3 Up

When you hear a ring pings, press start and press "A". Or press "Z" and go back to title
and then go down the list 2 times when you're in the intro of SONIC 3. You'll see options
go there. Now you can choose whichever you want.

This works if you also have SONIC 3 & KNUCKLES.

CIAO!! XD