2019-08-23
Protection from a player means that the permanent has protection from each object controlled by that player. If an object has no controller (such as a card in a graveyard), its owner is considered its controller for this purpose.
2019-08-23
The players that the target permanent has protection from are determined as Cliffside Rescuer's ability resolves. If an opponent somehow gains control of that permanent later in the turn, it still has protection from your opponents, including its new controller.