You can get them from game stores like GAME or Gamestation. Remember that there's no such thing as a 'DSi XL' game, they are just 'DS games', though there are a handful of games that only work on DSi, there's none that are XL-only.
Yes, DS games do work in a DSi XL. The DSi XL is part of the DS line, so DS games are meant to work with it.
No. 3DS games are not compatible with the DSi XL.
Of course!!! The dsi XL is just a bigger version of the dsi.
You download them from the DSi shop, accessed from the DSi or DSi XL's menu bar.
All of the games that work for any DS will work for DSI XL.
yes you can
No, the DSi XL does not have a slot-2 for GBA games.
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)
the XL is bigger and has 3 pre loaded games on it
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 yes you can
DSI XL a larger DSI