Neither. "Come when you may" means "whenever you arrive," so it's an adverbial temporal clause: it says when you'll be welcome.
The sentence "Come when you may." is an imperative, although an exceedingly polite one, meaning: "You must come but you may choose the time." A concessive clause allows for some contradiction to the main clause: "Although you may not wish to, come anyway."
I'm going to say that #2 is a concessive clause. The most common of these is introduced by words like "although" and "even if," but the defining characteristic of such a clause is that it presents some opposition to the idea of the main clause. It's called "concessive" because it concedes a possible error in, exception to, or difference from the claim of the main clause. Here you're the excepti
I think you are weary, and I don't want to badger you anymore tonight, so I will ask you what I'd like to question tomorrow. Have a good night deadrat.
Yes, certainly. Since "whatever" says that you don't know what's coming, you can't know whether it's something that can have intentions. Either #3 or #4 will work.