They exist, of course; however, one should consider what each letter represents. Sonic 3A: The original release. We've all played this. Also known as "Sonic 3 part 1." Sonic 3B: The lockon release. We've also played this. Originally known as "Sonic 3 part 2," and later changed to "Sonic & Knuckles." Sonic 3C: This. A full, pre-locked on version of Sonic 3 with everything in it. This is what you'd be able to play from locking on both parts of Sonic 3, and was meant to be distributed on a 3MB cartridge along with the other two releases. However, this never saw the light of day—until now, anyway. Sonic 3A is not in this batch. However, Sonic 3B is. I haven't seen the latter yet, though.