This is a prototype version of Sonic the Hedgehog for the Sega Game Gear. 'World' suggests a potential international release.  Details about the differences between this prototype and the final releases may vary.  Generally, prototypes might feature different levels, mechanics, or graphical elements than the finished product. Published by Sega.

Sonic The Hedgehog (World) (Proto)

Sonic Spinball (USA, Europe)