about a year and a half
any ds or 3ds game can be played on any 3ds system.
There is generally no age limit to own a 3DS.
You can play Nintendo DS and DSi games on the 3ds, but the 3ds doesn't have a slot on the bottom for Gameboy games.
Nintendo 3DS release for some days now, and there are many flash cards can break 3DS well, such as M3i zero, acekard 2i , R4i 3DS, supercard dstwo,i will recommend you M3i zero, it is one of the old and best card, and it is updateable, and will never blocked by Nintendo.There are many 3DS card in the market currently. such as 3DS card, R4i 3DS, R4iTT 3DS, R4i SDHC 3DS, R4 3DS, Acekard 3, M3i Zero and so on. All of them can run DSi games on Nintendo 3DS.
Assuming you mean old DS games, yes, the 3DS can play any of them, as long as they do not require Slot-2, like Guitar Hero.
Yes they do work but I wouldn't recommend using them or else Nintendo will brick your system. Currently, there are many R4 3DS cards which can on 3DS console, such as R4i SDHC 3DS, r4i gold 3ds, acekard 2i and so on. But all of them can only run DSi games, no r4 3ds card can run 3DS games.
YES
The 3DS XL came after the 3DS.
Yes no metter what 3DS is a 3DS
There is no such thing as a 3DS DSi.
No, it is not out for 3DS.
Save up money, do work for people around your neighborhood, ask your parents to get it for you for your birthday, or maybe you could lower your expectations. The 3ds is what, 250 dollars?