Sonic Chaos was internally named "Sonic the Hedgehog 3" early on. Build strings in the available prototypes hint that development began around early 1993.
The game was initially revealed at the 1993 SCES, which ran from June 3-6.
Sonic's design here is consistent with the May 17 Game Gear build. The HUD has the rings on the top with the time on the bottom. The area seen here in Turquoise Hill Zone also looks quite different than the final.The trees also have a darker tint much like the grass.More darkness seen.A shot of Tails with Sonic's life icon.