The Find Familiar spells allows a magic user to summon a spirit which takes on an animal form to serve as a familiar. If it is defeated, it disappears, and can be resummoned by casting the spell again.

The Pseudodragon is said to be sought out by mages, for it serves as a superior familiar if it can be befriended. 

Does this mean that a mage can befriend a Pseudodragon, gaining a familiar, without having the Find Familiar spell?

Does the Pseudodragon have the same abilities (delivering touch spells, pocket dimension storage) as the familiar from Find Familiar?

If a Pseudodragon is killed, can it be brought back with Find Familiar, or is that exclusive to the 'spirit' familiar from the spell?

An acceptable answer would highlight what is specifically unique to the Pseudodragon familiar, if anything.