Sonic the Hedgehog 2 (Aug 21, 1992 prototype) - Hidden Palace

A prototype of Sonic the Hedgehog 2 for the Sega Mega Drive.

Sonic Prototypes (released by Hidden Palace)

Sonic's a superstar on RYM - Rate Your Music

New Sonic game prototypes found by drx, shows early stages from Sonic CD, more to come

A story that gave a developer a pirated version of Sonic the Hedgehog 2 to developer Yuji Naka - GIGAZINE

Sonic the Hedgehog (1991) prototype discovered - The Independent Video Game Community

Tom Payne and the Box of Sonic 2 Development Disks – MegaBites

Sonic the Hedgehog CD (Mega-CD prototype; 1992-12-04) - Sonic Retro

Resumo e Imagens das novas prototypes dos jogos do Sonic

Sonic the Hedgehog 2 - Wikipedia

Sonic the Hedgehog 2 (Aug 21, 1992 prototype) - Hidden Palace