Yes they have an otomatone, what of it?
Also the species of demon their parent is from are formed coiled around a gem; Folly was born that way too. Their gem is basically a part of them, they hate to be separate from it and need to have it nestled into the curve of their tail. (I forgot to put it in my last comic whoopsie)
Folly rarely removes their mask. There’s only a few circumstances they would ever do that in.