Sonic 2 Advanced Edit Release 4 is likely a later version of the ROM hack, building upon Release 3 with potential bug fixes, added content, and further enhancements to the level design.  It likely continues the core gameplay of Sonic the Hedgehog 2 but with extensive alterations resulting in a unique experience.  The 'Advanced Edit' suggests it includes more substantial changes compared to minor ROM hacks.  The project is fan-made; it is not developed by Sega or Sonic Team.

Sonic 2 Advanced Edit Release 4

Sonic 2 - Score Rush