Sonic 2 XL is a hack of Sonic the Hedgehog 2 for the Sega Mega Drive/Genesis by Captain Bozo and Ranger. Rings are replaced with onion rings, and Sonic becomes fatter after eating them.

Sonic the Hedgehog 2: Pink Edition is a character swap hack of Sonic the Hedgehog 2 for the Sega Mega Drive/Genesis, with Amy Rose and Cream the Rabbit replacing Sonic the Hedgehog and Tails respectively. Amy Rose's sprites are designed after her modern look. Amy Rose with classic-style sprites is available to play in the Amy Rose in Sonic the Hedgehog 2 hack. The game was modified by Sonic Retro Member E-122-Psi, with additional programming and coding by other members including MarkeyJester, MainMemory, FraGag, Selbi, and Hayate. Most programming unique from Amy In Sonic 2 such as Cream the Rabbit's gameplay was implemented by Flamewing.

Sonic the Hedgehog 3 (ソニック・ザ・ヘッジホッグ3 Sonikku za Hejjihoggu Surī?) is a 1994 platform video game in the Sonic the Hedgehog series for the Sega Genesis. It was developed in the United States by members of Sonic Team working at Sega Technical Institute, and was published by Sega, debuting worldwide in the first half of 1994. The game is a sequel to the Sonic the Hedgehog 2 for the same system and follows on directly from the end of the game, in which Sonic defeated his enemy, Dr. Robotnik; crash-landing on a floating island, Sonic encounters new character Knuckles the Echidna, and must once more retrieve the Chaos Emeralds while also working to stop Dr. Robotnik from relaunching his ship, the Death Egg.The game is closely tied to its direct sequel Sonic & Knuckles, as the two games were originally developed as a single game until time constraints and cartridge costs forced them to be split into two interlocking parts.

Sonic the Hedgehog 3 (Nov-3-1993 prototype)...You can get more information's about this prototype in the hidden palace website, here is the link:https://hiddenpalace.org/Main_Page

Sonic the Hedgehog Genesis (Genesis) is a hack of Sonic the Hedgehog by Xenowhirl which attempts to recreate certain aspects of the Game Boy Advance Sonic 1port titled Sonic the Hedgehog Genesis.

Sonic And The Mystic Gems (previously known as Sonic 1 Harder Levels) is a hack made by Eduardo Knuckles and his team Harder Project of Sonic the Hedgehogon the Sega Mega Drive/Genesis. The hack adds to the game a lot of new features such as the three known main playable characters, a checkpoint monitor, customizable level music playlist, a sweet and clear save data select menu, difficulty selection, a unique music menu and some other additional menus and screens which gives to the game a completely new gameplay experience.

Sonic the Hedgehog Megamix (commonly shortened to Sonic Megamix) is a work-in-progress multiperson disassembly modification of the original Sonic the Hedgehog videogame for the Sega Mega Drive / Genesis, developed by Team Megamix and more recently moved to the Sega Mega-CD. The game features the ability to play as one of five different characters: Sonic the Hedgehog, Mighty the Armadillo, Shadow the Hedgehog, Miles "Tails" Prower, and Knuckles the Echidna. It is an extensive reworking of the original game, featuring new art, music, abilities, layouts, and other things.