Bonjour
the correct question is the first one =
Avez-vous fini le repas avec du dessert ?
in the 2nd one, the 'trait d'union' (hyphen) is missing between avez & vous
in the 3rd one, there's an extra 'trait d'union' between vous & fini..
you must use the 'trait d'union' only between the verb and the subject pronoun == avez-vous ... ?
hope this helps ☺☺☺
