No. the 3ds games have a tab on them so that they do not fit into another ds, if it went in, the game might break the dsi.
No. The 3DS is region locked, EU games will not work on a US 3DS.
No, 3DS games only work in a 3DS or 3DS XL.
No, 3DS games only work on the 3DS and 3DS XL as well as the 2DS
no
Yes
No. Currently, as of February 2014, the 3DS is the DS with the best and up to date features
No, 3DS games will only work in a 3DS.
No, they only work on the 3DS platform. But, you can play DSi and DS games on your 3DS.
Yes, dsi games works on the 3DS also DS games work on the 3DS.
No, the 3DS is region locked.
Yes. In fact, it will have additional functionality on the 3DS and the DSi series
No, dsi games work in a 3ds, wont appear 3d though, but the dsi does not have the ability to play 3ds games.