Here is the full list of all 4 Rainbow Laser Disco Dungeon Demo achievements. It takes around 0-1 hour to unlock all of the achievements on Windows.
Finish the demo? You did it! Like "did it" did it. Can you dig it?
You did it... in Safety Dance mode. S s s s A a a a F f f f E e e e
You completed the Tutorial! You probably know how to play now.
You're actually playing it! Nice!