Probably; he has for all the others.
I think the Isshu region is the same as Unova. And, no you can not trade pokemon from Unova/isshu to any other region because the older games have no data on the new pokemon.
catch it
unfortunately, you can't catch it in any Pokemon game, you could only get it during an event. but, you can trade for it with your friends or in the GTS (Global Trade Station). the GTS is on the second floor of any Pokemon Center (not at the Pokemon League, though) and it is the man on the far right. :) good luck!
Isshu doesn't have any new Eevee evolutions but Eevee is capable of evolving into any of the previous evolutions which includes Glaceon and Leafeon.
You can not catch any Pokemon in Pokemon soul silver. the ones that are not in there must be traded. Hope i helped.
Yes, you can use any Pokemon in the Pokemon league.
You can't catch any starter pokemon in any pokemon game. But you can trade them online via GTS.
You cant catch any trainers Pokemon
no
No. How can you catch a Pokemon if you cant weaken it. In Pokemon ranger though you can capture your partner Pokemon.
You cannot catch a tiranitar on any pokemon game, you have to get him from evolving Pupitar.
Well, now your free to catch mostly any Pokemon available to you in the game depending on the game that you have. Try training some of your Pokemon to battle other people via wi-fi connection.