Sonic 2 Lost Worlds

Sonic The Hedgehog: The Lost Worlds is a hack of Sonic the Hedgehog 2 by ExecByte. This hack features all of the zones that were cut from Sonic 2 during development. Some zones have been ported from the Sonic 2 Simon Wai prototype and then finished up, and some have been created based on magazine pictures and information from interviews with people who worked on Sonic 2.

Levels:

• Dust Hill Zone
• Rock Zone - The music is Mystic Cave Zone 2 player.
• Wood Zone - The music is the beta version of Metropolis Zone
• Winter Zone
• Hidden Palace Zone - Background music is the intended music for the level. Mystic Cave boss is used with the only alteration that the sequence of picks and rocks is omitted. Also, the bat badniks are utilized, which ended up being unused in the final Sonic 2
• Casino Night Zone (Sonic 2 Beta style) - Music is the beta music
• Cyber City Zone - The music is 2 player Casino Night Zone

Source: http://info.sonicretro.org/Sonic_the_Hedgehog_-_The_Lost_Worlds