Sonic The Hedgehog 3 & Knuckles (lost build of cancelled iOS port of Sega Genesis platformers; 2014) - The Lost Media Wiki

Super Sonic (lost build of cancelled Sega CD port of Sega Genesis platformer Sonic the Hedgehog 2; existence unconfirmed; 1992-1993) - The Lost Media Wiki

Sonic at the Olympic Winter Games (found iOS game; 2010) - The Lost Media Wiki

Sonic & Sega All-Stars Racing (lost prototype builds of multiplatform racing game; late-2000s) - The Lost Media Wiki

Sonic The Hedgehog: Awakening (lost build of cancelled Sonic the Hedgehog game; existence unconfirmed; late 2000s) - The Lost Media Wiki

Sonic the Hedgehog 2 - Wikipedia

drth d56 trh by fredefermaso4 - Issuu

Sonic Triple Trouble (lost Master System conversion of Sega Game Gear platformer; 1994) - The Lost Media Wiki

Editing Mario & Sonic at the Sochi 2014 Olympic Winter Games (lost build of cancelled 3DS version of Wii U crossover sports/party game; existence unconfirmed; 2013) - The Lost Media Wiki

Sonic & Knuckles Collection - PCGamingWiki PCGW - bugs, fixes, crashes, mods, guides and improvements for every PC game

Super Sonic (lost build of cancelled Sega CD port of Sega Genesis platformer Sonic the Hedgehog 2; existence unconfirmed; 1992-1993) - The Lost Media Wiki

Sonic 3 & Knuckles (Video Game) - TV Tropes

Editing Sonic the Hedgehog 2006 (lost build of Tokyo Toy Show tech demo of multiplatform platformer; 2005) - The Lost Media Wiki

Sonic CD - Wikipedia

Sonic the Hedgehog 2 - Wikipedia