Yes, you can get 100% in the demo!
Yeah the mushroom hat is not a glitch. (And tbh most ACTUAL glitches are pretty much intentional at this point.)
Oh, the stone tablet. Some EMUUROM could be of help for reaching the lookout tower from below....
Keep on scanning! More coming later this year. :D And thanks for the comment, your kind worlds made me feel all warm and fuzzy inside :]