Spells or abilities that can target "up to" any number of targets can be legal targets for "Magic Rebound," provided they only select one target in total.
This card can change the target of an opponent's spell to a Barrier J/resonator they control (if it is a legal target), as the Barrier keyword doesn't prevent a player from targeting their own J/resonator and "Magic Rebound" only targets the spell or ability.
Although spells can't target themselves, "Magic Rebound" can be used to change the target of a spell that targets another spell on the chase (such as "Keen Sense" or "Seal of Wind and Light") to "Magic Rebound," as long as "Magic Rebound" is a legal target for that spell.