Vulcan the Divine Rulings explained

Q: If Vulcan the Divine targets 2 cards and one of them is not on the field anymore when its effect resolves, will the other one be returned to the hand?
A: Yes the other card will still be returned to the hand.

Q: If Vulcan the Divine targets 2 cards and one of them is not face-up on the field anymore when its effect resolves (like being set by Book of Moon), will the other one be returned to the hand?
A: Yes the other card will still be returned to the hand.

Q: Can Vulcan the Divine target a face-up Continuous/Field/Equip Spell/Trap or Monster card that has activated its effect during that same turn?
A: Yes, it can target it.

Q: If Vulcan the Divine targets a card that has activated its effect during that same turn, and that card doesn't end up returned in the hand but is either banished or sent to the graveyard/deck, can that card's effect be activated again later that same turn?
A: Yes it can be activated again.