

Sonic 2 Addendum it aims to create an enhanced, definitive version of the original game by restoring and reimagining content from unused beta versions and prototypes, alongside adding modern quality-of-life improvements.

The project reimagines the original West Side Island adventure with a narrative focused on Dr. Robotnik’s "terraformation scheme," which has transformed classic zones into surreal, expanded environments filled with new secrets and branching paths.

A hack which combines Sonic 1 levels, Sonic 2 (final and prototype) levels, Sonic 3 levels, and Sonic and Knuckles levels into one game.

“Sonic The Hedgehog 2: Archives” is ‘another beta hack’ that seeks to bring back cut content from the game's Prototypes, revitalize the game's concept and release levels and badniks, and fully recreate the early concept of the time-travel story. Along with this hack improves both the prototype content and the final content by adding new animations, badnik and character shots, level art and backgrounds, new music, and more.

Sonic 1: South Island Definitive is a hack by RadiantNexus Team, which seeks to reimagine Sonic 1 by rearranging levels. remixing music, adding features from future games, and readding scrapped ideas in new and interesting ways. Major features: 3 acts of reimagined level design, including one act that has yet to be fully reimagined in any other hack. A miniboss. Massive art overhaul all over the place. Music made by ProjectFM and MechaKnuckles. Menus! A custom splash screen. There's been massive engine overhauls as well, including the Sonic 3 level layout format for massive levels, and the Sonic 3 object manager to go alongside this.

Released on Sega Mega Drive/Genesis, by Jdpense.
Released on Sega Master System/Mark III, by DarkTheCreature.

Released on Sega Master System/Mark III, by Red Miso Studios.

Sonic the Hedgehog: Proto-Mix is a ROM modification for the 2013 mobile/RSDK version of Sonic the Hedgehog. The hack is defined by its objective to "mix" the high-speed gameplay of the final 1991 release with rare, scrapped elements found in early prototype builds and magazine scans.