The 3DS itself has a universal friend code that is used on all the 3DS games and applications the player uses. It means they only need to add a friend once, by adding their 3DS code, they can play multiplayer in any 3DS game that supports it.
For regular DS games, it is the game itself that has its own code, so you'd register your friend's Soul Silver friend code on your own Soul Silver, etc, whether you play it in a 3DS or the older models.
You could not though add someone's Soul Silver code to the 3DS friend list.
No, the Nintendo DS lite cannot play 3DS games.
No, you cannot register a Nintendo 3DS from a different region.
actually nintendo has no plans for making a nintendo 3ds.
The DS lite is almost exactly the same size as the 3DS.
there is not confirmation that there will be a 3DS XL or Lite, but i thing i read about 3DS lite somewhere.
no
no only nintendo 3ds
About the same as the DS Lite
Yes, the Nintendo 3DS (as well as the 3DS XL and 2dS) has its own 3DS games that will not work for the Nintendo DS, Nintendo DS Lite, Nintendo DSi, and Nintendo DSi XL.
Well if you have seen how big the nintendo ds lite is that is how big it is. :-)
Handheld: None announced so far, probably the Nintendo 3DS Lite. Console: Wii U.
you used to but you can't get that offer anymore