Can Rebuttal counter or take control of Starfall?

Yes — Rebuttal can target Falling Star (there's no card named "Starfall" in the database; if you mean the Fury spell Falling Star, it has Energy cost 2, which is within Rebuttal's "no more than [4]" limit).

When Rebuttal resolves, you choose then: pay [A] to take control of Falling Star and make new choices for it (you can retarget either or both "Deal 3" instances, including onto the opponent's own units), or decline and simply counter it. You don't have to commit to the [A] when you play Rebuttal — it's a cost paid on resolution (FAQ 12038).

One catch: Falling Star must still be on the chain when Rebuttal resolves — if it's already been countered or removed, Rebuttal fizzles and you keep your runes.