Question 1: The Kyurem you catch does not have any EVs, like any wild Pokemon that is freshly caught. Start EV training, you've got nothing to worry about.
Question 2: If it did, you would have to.
Question 3: A person in the game gives them to you. Or you can get them in the Dream World.
Question 4: I was having a hard time finding one to give you EV reducing Berrys. This one gives you all Berrys, plus a bunch of other stuff. Source
DISCLAIMER -
ALL CODES ARE WORKING AFTER YOU GET YOUR FIRST POKEMON
I REPEAT DO NOT TRY TO USE/SORT THEM UNTIL YOU HAVE ACQUIRED 1 POKEMON (YOUR STARTER)
(Press Select)
x999
Essential (not all) Medicines
ALL EV/IV Boosters - Wings + Vitamins
All Berries
All TMs&HM's
94000130 FFFB0000
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D2000000 00000000