We apologise for the late review:
I am partial to racing games or anything related to cars, so your game immediately caught my attention. I like the idea that you have, but the controls and visuals need a bit of work to be easier to understand and navigate. The car reacts a bit slowly, and the Nitro boost also has some lag before it registers so the timing can be difficult for the casual players you are targeting. The spinning obstacles also make the timing of when to use Nitro harder. Your car design is good, and the procedural generation of the enemies works well. Otherwise, the art and models are pretty basic and could use some improvement. The GDD says that you can fall into the void and that it loses you hearts, but I kept bouncing off the edges: whichever one is the intended behavior needs to be described and implemented.
Waiting until the day of submission to make your GDD defeats the purpose of a GDD: it serves as a guideline and place to organize your thoughts about how to design and develop your game. I suggest that you start with a basic GDD to start and add goals and changes as they happen. Your proposed development timeline seems fine and logical, and recognizing and noting that you didn't follow that timeline is good. Otherwise, your GDD is very basic and does not offer a lot of other information than the absolute minimum of listing the mechanics (not even talking about the controls or what they do).
I hope that you continue development on this game and take it forward into the game style that you enjoy. I know that game jams have the "calm peaceful atmosphere of hell," so I hope that you didn't burn out and that you can cross your own finish line.