This is a great model for a character like OVA sonic- since its a model and not a character mod, I'll try to translate the "two components" system best I can with a model, here it goes!
[Faithfulness]: To clarify this means both to the design and sprite's its based on and how well the model translate them both, for a first model it does it extremely well! I think the low-poly aesthetic works here for the design as a whole, translating OVA sonic's nice design in a low poly package best it can! its just so cute, just look at the little guy! comparing to the sprites I think it does a BETTER job at times (no shade to the original spriter here) such as the dash mode peel out, the spin ball, and the wall run (which is original when compared to said sprites which I love!). really solid job here all around, not much to complain really.
[Flow/Feel]: This is for how the model feels when looked at during gameplay and how it feels to control overall in the 3d space of this game, if that is the case this model also does an outstanding job! the sprites already did a good job of this and I think this model does it justice here, it feels super good to play with especially with the animations and some of the extra touches made by you! (wall running) since this is your first model I can't really complain to much on this section but I would enjoy a bit more of an expressive walk cycle, all things considered the sprites had a pretty unique walk and filled with a lot of energy, it is present here but the arm pumps feel a little more... basic? in comparison, it could have been just the transition to a model but if anything this a very minor nitpick so don't take it too much to heart.
All in all this is what I felt about this model, I think this is a really great start for you and I'm glad I personally was able to help in its creation as well, even if it wasn't modeling tips or something- I hope a good future for you and your career as a 3D modeler!
You make really good points, looking back on him today, he could use some more expression in his poses, though that's mostly due to my inexperience. I'll likely improve animations with later updates.
Also, you have it almost on the nose with his whole idea, meant to be a combination of the OVA design while also being accurate next to the original sprites, with some personal choices thrown in there for good measure. I'm glad you enjoy the model!! Thank you so much for the feedback, yet again. I hope for a good future for you as well, my friend <3