Most classic Sonic hacking focuses on the Genesis trilogy (Sonic 1, 2, 3 & Knuckles). Tools like SonED2 and SonLVL are mature. However, presents unique challenges and opportunities:
polished the experience, the ROM hacking community has taken it even further, restoring lost features and adding modern mechanics to this 16-bit masterpiece. Sonic Cd Rom Hacks
It’s designed for high-level speedplay and is widely considered the most "polished" mod for the game. Sonic CD++ (Plus Plus) Sonic CD Plus Plus - Sonic Retro Most classic Sonic hacking focuses on the Genesis