Pretty sure you can submit anything you want, untill you want to do the open source stuff. Freecodecamp is just here to help you learn, not choose what you learn
Why do you want to use a game framework when you definitely should learn to write game engines? It helped me a lot when started to learn programming in general ~25+ years ago … well, yeah it can’t help me a lot with this CSS madness, but the basics in some specific areas are very welcomed
My whole design in learning JS was to actually write plugins for this specific game engine. I understand the appeal of scripting my own, but I am pretty invested in at least finishing the game I started in this one. It would be super cool if I could submit a plugin scripted game for my last two projects because that would be killing two birds with one stone for me.