Congrats on completing your project in one week. No matter the game, it's an accomplishment :)
I'm sure a lot of the feedback you will receive will sound obvious, but hearing it from other people can help reinforce your learning for the next game you make.
The core concept here is worthy of a game. Adding some sort of score or timer at the top of the screen would take this from a little demo to feeling more like a complete game. Also, I'm not familiar with GMS2, but it's a totally valid game engine for jams. No need to qualify your answer to the second question above :)
It looks like you're using a timer to subtract an amount of rotation from the dial, right? Could you adjust your code to set an update point at an interval, then every frame, rotate slightly towards it? That might make the random rotations feel a lot smoother and help your game feel more polished.
Again, congrats on finishing this in a week. I hope you keep jamming and keep making games!