Somari 64 Sonic is likely a custom ROM hack for the Nintendo 64, possibly blending elements from both the Sonic the Hedgehog and Somari game series. Gameplay would depend largely on the specific elements incorporated from each title and the hack creator's vision.  This is a fan-made game and not officially supported by Nintendo or the original game's developers.

Somari 64 Sonic

Snowboard Kids 2 (Australia)