Originally uploaded back in 2011 by Aerobian-Angel.
It was made in Flash CS4 and was a celebration of Sonic's 20th Anniversary.
Animator's Youtube page: https://www.youtube.com/c/AerobianAngel
Animator's Twitter page: https://twitter.com/Aerobian_Angel
Music: "North Wind" (aka "Sonic vs Knuckles") from Sonic the Fighters
Link to the original flash version: https://www.deviantart.com/aerobian-angel/art/Sonic-vs-Knuckles-Part-1-215160202
This is part of Sonic Paradox's Flash Archive. With Adobe Flash shutting down the Sonic Paradox team wanted to preserve some of the Sonic Flash animations in full 1080p.