There's a hack called sonic 3 complete, and it alters things Juuuuuuust right so it's even better, you can activate instashield without going super/hyper, they replace the super sonic theme with a sped up level theme so you can still hear the level theme, the fixed the egg robot sprite in flying battery, they added an intro cutscene to knuckles' route, you have the option of putting flying battery after carnival night and the door from it becomes the snowboard in ice cap… nice bits of polish that while the lack of them never ruined the game or anything, they're really nice touches to have. Oh! and they also put back in the sonic 3 final boss. As well as a few sonic 3 tracks that go away when you combine games.