Most pokemons (If not all) might have a hidden ability upon capture/taking/whatever... (That's why you got it ^^)
I agree with the above statement though (Sorry :x)
Sylveon can't learn that too (And he should). I don't know if it's something wrong with the move itself or the pokemon. Have you tried Noivern, if he can learn it?
That's how you do it for most fossils (I think only Gen 5 fossils are different). Just save in front of the rock and keep resetting until you get the fossil you want (Might take a while... Probably will)
Really good pokemons i.e "pseudo legendaries" probably will not be available for a while. Because (Ame is not that nice...) the game would be easier with better pokemon...
I remember i almost killed Solaris Garchomp: Psybeam confused on the first turn, and the focus band on my Alakazam activated like 5 or 6 times ^^ (If it weren't for the Full Restores...)
Probably Ame didn't code it for people that already did the trade. That's what i'm willing to bet (Although in my opinion, a Riolu is more useful than a Darumaka. Sorry ^^)
Well, if you are going for Ralts, get a Modest one, or it's going to be a failure like shofu's. (Yes you got a major ripoff. Blame Amethyst, you can always blame her)
Gyarados is a very good addition to any team (It helped me in three gyms). You just need the pacience (I played on episode 9 so i got it for 3000$. So you got ripped off ^^)
I'm pretty sure Teddiursa roams around Peridot Ward, in a "Hide & Seek fashion". (You found him a bunch of times before battling him). Also, he only appear on when the weather is clear, so yeah ^^