This is one of the best I've played! It has an incredible presentation. The models are cohesive and well placed and the sprites fit perfectly in the style that you want to recreate. Having great 2D and 3D design is something really special. You nailed an immaculate vibe that every videogame player has experienced and of course reminds us to simpler times.
As the fighting training has not enough reaction time for the button sequences (I'm not sure if that can be improved training in other way), the best way to grind is the speed training. I'm not the biggest fan of grinding, but I could feel more encouraged to do that if I had a clear goal. I know that the goal is to improve your skills to performance better in the race, but it feels like "keep training until something different happens".
I understand the way you used the 3D environment to recreate the feeling of playing videogames in long trips, but it feels irrelevant once you start playing in the Cheese-Boy. I think it would've been nice if you'd find a way to mix 2D and 3D gameplay. Don't take that as a complain, I know there's a time limitation in the jam, but I think you have incredible skills to twist even more the premise of the game.
This was a really good entry, be sure that you made it incredibly well!