Yes it is. I have the game, a dsi, and the game works with it.
No. The DSi is region locked.
No, it doesn't fit into the slot.
Yes, since the DSi and DSi XL are the same, software-wise.
It is compatible with all DS games apart from any that require Slot 2, which the DSi and the XL do not have. (There is no such thing as a DSi XL specific game.)
yes
No. 3DS games are not compatible with the DSi XL.
No, the DSi is only compatible with DSiWare.
Yes, all DS games are compatible with the DSi.
No, the DSi XL is wi-fi compatible as is.
There is no "DSi lite" console but if you mean the DSi XL, it is fully compatible with DSi games(although you'll have to buy them twice if you want a copy on a DSi and a DSi XL)
no.....
No, Pokemon Black and White are compatible with all versions of Nintendo's DS line.