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.
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.
A 3DSc can play NDS and NDSi games
YES
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.
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.
Sorry no you can't the 3ds cartridge has a small bit sticking out and has 3d software on it Love miss 10 year old
Whether you get a 3DS XL or a tablet depends on how you entertain yourself. If you must have the graphic you should go with the 3D XL. If you can deal with so-so video games and will get use out of all the apps that a tablet has to offer, then go for the tablet. I would choose the tablet.
If your r4i gold Edition is old version, it has to be ugraded in a DS lite to support 3DS or DSi V1.42 console. But if it is new, it can work on Nintendo 3DS, DSi V1.4.3 or DSi V1.4.2 straightly. No need any update.
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.
any ds or 3ds game can be played on any 3ds system.
Unfortunately no, Guitar Hero: On Tour and it's sequels cannot be played on the Nintendo DSi, Nintendo DSi XL, Nintendo 3DS or Nintendo 3DS XL. All these systems do not have Slot-2 hardware (Game Boy Advance slot), which is the main requirement for this title.
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.