Apple manufactures all their own devices. They don't have any incentive to do so nor any way to do so since they're not dealing with 3rd party phone manufacturers.
B) Not dealing with 3rd party manufacturers seems unrelated to the discussion. Can you expand?
B) Apple controls the entire supply chain for iPhones. They have no need from a profit standpoint to try and insert hardware that allows other companies to do anything to their users. The secret backdoors are almost always the result of some exchange - FB offers data about users in exchange for the ability to insert hardware/software into a phone. Since that exchange doesn't exist for Apple, there's no reason for it.