yes immidiatly.
yes
yes...
yes you can
trade from Pokemon diamond/pear
No
Trade from pokemon soul silver or another pokemon game
you have to trade it from diamond to soul silver and you can't actually catch Roselia wild in Pokemon soul silver.
yes
YUP
yes
Yes, just trade it from Pokemon Diamond or Pokemon Pearl.
Go to the Union Room.
To get both leafeon and glaceon in Pokemon soul silver or heart gold you have to trade it from diamond pearl or platinum.
you can trade it at any time A BONGONA BASHTI [joke]