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Immune and protect abilities target the cards that gain the immune or protected status.
Yes, he is protected from discard and capture that turn. Why would you think he wouldn't be?
An ongoing ability, depending on the targeting of the particular ability, updates its targets while it remains ongoing.
If an instant ability is prevented, it cannot later activate if the prevention is negated. Ongoing abilities will activate if the ability preventing them is negated.
An ongoing ability, depending on the targeting of the particular ability, updates its targets while it remains ongoing. If an ongoing ability is prevented from activating, but the ability that stopped it from activating is later negated, then the ongoing ability activates and updates targets at that moment.