(1) region exclusives as you said, need to travel
(2) Legendaries, still not released in the game, speculation is saying that this summer we gonna see the first legendary events, don't know if all around the world, only in major cities, only with previous Niantic invitation, etc...A lot of questions with this ones...
(3)
201. Unown, the hardest one to find, their spawn is something crazy like 1/6 milion or something like that, but they are in the game, they have 26 different forms, you earn a badge with your progress towards the 26 forms (my guess is that they will be part of an special event too, so don't worry if you can't find them, they just want to hype them because they are nothing special a part from the 26 forms)
225 & 235. Delibird and Smeargle, they are not in the game yet because they have special moves, Delibird move is "present" which either can damage or heal the target mon, they are for sure trying to figure out how to implement that move, that is the reason why is not in the game. As for Smeargle the same, his special move is "sketch", which copies the enemy move, still not implemented in the game, a similar behaviour they can try to use is ditto, which copies both of the mon moves a part from their physical shape, but Smeargle is different as he not transforms into the mon.
