Pokemon Black Version 2
This game can be played on its own and is a really good game. I would highly recommend Pokemon Black in general too.
If you buy the English version it will be in English.
It'll be used, the only place to find a new copy would be ebay and it would be more expensive since it's an out of print game.
Yes, as long as you have the Poke Transporter installed on your 3ds and a copy of the game it will work.
No. It comes in a little square bag.
Yes, all dsi games are compatible with a 3ds/3dsXL