Keep Circulating the Tapes: The game has never seen a re-release outside of GameTap for a brief period, and it's unlikely to get another one anytime soon.
What Could Have Been: There is evidence that this was originally going to be the cancelled title, Sonic Crackers. More specifically, the ring tether mechanic was present in a working form and the animations used for Mighty are very clearly drawn over Sonic's animations from the Crackers proof-of-concept (he even has the same Wheel o' Feet effect despite his primary character trait being his strength).
It was originally going to be included in Sonic Gems Collection at one point, but was dropped, probably because of issues emulating the 32X. However, an entire mini-gallery of art from the game was included in the Museum.
One beta screenshot of the title screen implied that Espio was supposed to be the main character or a major player of the game, with Knuckles just tagging along.
An early working title for the game, proven by a beta screenshot, was Knuckles' Ring Star.