Probably the only Sonic CD hack around but Sonic CD Plus Plus is a hack created by quii and snkenjoi where it esentially improves the quality in terms of gameplay by adding new features to it which includes a sonic 2 style spindash implemented into the game, much as to how you can in the 2011 re-release of sonic cd for android and ios. other features includes a Sonic Megamix style homing attack, as well an air roll move that give you the chance of being able to avoid getting hit by enemies along with the speed cap being removed. none much else to say so for those who wants to play this, you can get it down below for your matching region.
US: http://info.sonicretro.org/images/1/12/SCDPP_%28U%29.7z
EU: http://info.sonicretro.org/images/9/9b/SCDPP_%28E%29.7z
JP: http://info.sonicretro.org/images/b/b8/SCDPP_%28J%29.7z