any ds or 3ds game can be played on any 3ds system.
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.
Normally, you can play new DS games on old DS. But if the games says for DSi only, or for 3DS(will be pubulished soon) only,the it can not play on old DS.
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.
A 3DSc can play NDS and NDSi games
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.
In the Sonic Boom New TV Series and video games for the Wii U and 3DS, He is now 23 years old now in 2014
It has a store that you can buy games in, sort of like the app store but at the sane time alot different.It's called the Nintendo Eshop. You can buy old school games such as gameboy or Nes, or buy 3DS Eshop games.
Pokémon X and Pokémon Y are for the Nintendo 3DS and thus cannot be played on a regular DS such as the original DS and the DS Lite and they also can't be played on the DSi or DSi XL however they can be played on the Nintendo 2DS.
June 6. the eshop will be awesome! there is going to be: netflix [i think], old games from the past [example: super Mario land, Kirby's dream land and more], trailers for new upcoming 3ds games, other 3ds game apps i don't know and last but not least: dsi ware [dsi ware can't be in 3d] the points will be like money from real life. don't worry!! a 3ds prepaid card or credit card can get you 3ds money.
If it's one of the ones that come with a game already installed, then you can transfer a 3DS profile to it and the XL's game will be added to your profile, it will not be overwritten. However if the new XL already has a profile (a Mii, etc) then anything specific to that profile will be overwritten, and anything on its SD card will be inaccessible.
Derek Jeter
You should wait for the PS4 to exist and have games before you want an answer to such a what if question. Based on the past when a new console is released the old one can not play the new console games. Why would you buy the new console if the old one could play the games.