I just wanted to stop in and say that this is my favorite thread on the forums.
On a side note, don’t use SEGA IP because it belongs to SEGA, and not anyone else. HTH.
I’ll throw you a bone.
SEGA has both IP rights (Intellectual property - Wikipedia) AND Copyright in the USA and multiple other countries to the Sonic Franchise, Sonic Assets, and hardware built for Sonic, among other things.
If you are serious about making a game you can go : Request a Search Estimate | U.S. Copyright Office and fork over a few hundred dollars to do what is called “Due Diligence” in the R&D world. After you have done your due diligence you will have your answer as to the nature of some of the posts in this thread.