I think playing around with free assets is a great way to hone your skills and practice. With that you, completed a game, made three fully playable levels, learnt some neat unity features like the fog, and everything without the hassle of making the assets yourself. I think you got a good grasp of the basics and I hope this was a good learning expierience. With that being said I will give you a few begginer tips that helped me a lot (being a begginer myself)

-First you should just zip the game files instead of doing an instalable. That way more people will play it. Many people are afraid or just dont want to install unknown stuff on their computers.

-In the main menu you can experiment a little with the buttons. You have done all the coding already! So you will see that adding a few buttons is a piece of cake and actually really fun!

-A trick I think some people dont know is that when you move around game objects (in this case the cubes you used for the laberinth) if you keep pressed the "V" key and touch one of the cubes corners it will snap to other game objects corners like "magnetically". This way you can paste two cubes perfectly aligned toghether!

Anyway, good job man! I hope you keep improving those skills!

As a base, it is pretty good. You got the animations rigged up nicely and the fog works nice as an added aesthetic. I'm assuming you will be working on this for the jam?