Sonic Unlimited v3.5 is a version of a fan-made game or ROM hack, likely an improved iteration of v3.0. Updates in version 3.5 might include bug fixes, new levels, enhanced graphics, or improved gameplay mechanics. The original Sonic game was developed by Sega.  These versions highlight the passion and dedication of fan developers in creating and continuously improving their projects, expanding the universe of Sonic.

Sonic Unlimited v3.5

Sonic The Return of Shadow