Angel Island falls at the start of Sonic the Hedgehog 3 (1994), Sega's Genesis sequel that adds save files and a story built to lock onto Sonic & Knuckles. Carnival Night, Ice Cap, and Launch Base continue the hunt for emeralds while Knuckles works against Sonic for reasons the cartridge only half explains.
Wii Virtual Console later reissued that 16-bit cartridge. The lock-on port on the follow-up cart is how this story was meant to finish, with the Death Egg still in the sky.
Save data was new for this hedgehog. The Virtual Console reissue is that same cartridge, island and all, not a 3D remake of the carnival.