From Wikipedia: Sonic Classic Collection contains Sonic the Hedgehog, Sonic the Hedgehog 2, Sonic the Hedgehog 3, and Sonic & Knuckles. The Lock-on modes from the original Sonic & Knuckles cartridge (Knuckles in Sonic the Hedgehog 2 and Sonic 3 & Knuckles) are fully implemented and playable. The ability to save and load at any point, a feature not found in the original games, is also present. Alongside the main games, a gallery of early artwork from the Sonic series is viewable.