From Sonic Retro
Magazine Preview #14 - Tails "Hybrid" Life Icon in a Sonic 2 Prototype Splitscreen
|Source: MegaForce, Issue #6, Oct 1992||Source: Sonic 2 Beta ROM|
Sonic no longer has the swirling legs in his running animation. Sonic and Tails both happen to have one ring, presumably because they're still sharing the same ring counter. One little detail:
Even though Tail's counter actually has Tails icon (in our prototype it uses Sonic's), the text next to it says "Sonic".
Clearly this is a newer prototype.