What should I do about this person who has hared me?

Trust your instinct when all else fails; in this case, it seems like your instinct is telling you to ignore him (and seem like a jerk), which I think isn't a bad idea. It sounds as if your "friend" B is somewhat jealous of you in some ways. Also, he seems to be up to no good with the ups and downs way he's been toward you since 4th grade. You are young and seem to be a very smart person, so I wouldn't worry about not being able to have friends who are genuine. It may sound easier said than done, but trust me, you'll do fine (if not better) without this troubled friend of yours. Focus on school and doing what YOU want and like to do because if you don't, you may someday regret it and you'll only have yourself to answer to. Good luck and be true to yourself.