At the top of the 3DS is a slot for cartridge-based games. Insert the cartridge here. On the 3DS' menu screen, typically the second icon on the first column, is the one for the inserted game. Select it with the stylus to play.
You buy ds or 3ds games and then put them in your 3ds.
No.
No... they haven't made gameboy games for 10 years.
No, you can't.
That is not possible. You can transfer DSiWare games from DSi to 3DS, but not the other way around.
No, you can't.
The Nintendo 3DS will be able to play Nintendo DS and DSi games but games published for the Nintendo 3DS will not be compatible with those systems.
Nothing, as a 3DS game will not fit into a Ds slot. FOr downloaded games you will not see it
No, 3DS games can only be played on the 3DS.
No, that'd mean the 3DS would be open to all manner of software piracy. The way to download games using it is over wi-fi, using the 3DS Store.
Yes. The Nintendo 2DS is built to play 3DS games, so the mini cartridges are the same as those used on the 3DS. The 2DS does not have its own library of games separate from the 3DS.
There will be an online shop called the eShop and I believe it will have downloadable 3DS games. But about the DSTWO part, I'm not sure if you'll be able to put 3DS games onto it. Just in case, you may wanna check the main site.