Yes, but only if something else follows. Otherwise, Maps’s suggestion is better.

Yes! Another way to say this is: "None of your business"

I'd say "It is not of your concern" or "It doesn't concern you" t'he segon one sounds nicer. You although can say "Is not matter of your business". Anyway ask a native speaker to be 100% diré 😉

Yes

You can say "it's not your concern "