Sonic's Timeline SRB2 Message Board

First of all I'll mention I wont count spinoffs as mainline cannon games (Sonic Rush, Mobile Sonic games, Sonic Racing games) I'll count the storybooks as the gameplay has kind of a development of an early boost (although as someone who played them I must say that those boosts were crappy)

Advance Sonic SRB2 Workshop

Sonic Robo Blast 2 PSP - GameBrew

Goo Sonic SRB2 Workshop

Sonic Robo Blast 2

Sonic Robo Blast 2 Kart - Sonic Retro

Cherribun's Stylized Sonic Model

sonic adventure 1997 prototype v2 (real) : r/SonicTheHedgehog

Sonic Robo Blast 2 (3D Sonic fangame in development for 20+ years) releases huge new update. [New July 2020 update.], Page 10

Release] Sonic Robo Blast 2 for New3DS, Page 3

Sonic Robo Blast 2: The Cyberdime Realm - Speedrun