This can be a number of problems, but send it off to Nintendo so they can have a proper look at it, or try recalibrating it (in the System Settings).
you need a wifi connection
Yes the Nintendo 3ds xl does have a camera.
you need 2 go on the ar card application find a light place and lay down the ? card on a flat surface below the light. then you aim the 3ds camera at the ? card. if you followed these instructions, 6 blocks should appear above the ? card on the 3ds camera. point the camera at one of them and it should tell you what to do from there. oh and by the way, dont bend them or use them to much or it wont work. another thing there are instructions on the 3ds that tell you how to use it so there was really no sense in writing all of this. hope I helped.
No, dsi games work in a 3ds, wont appear 3d though, but the dsi does not have the ability to play 3ds games.
Probably not, It is designed to "signifigantly curb" piracy and hacks, so that pirated cards wont work.
cause it is old
It will work on Nintendo ds lite, Nintendo dsi and on the 3ds. It wont be in 3d though
Yes.
yup
It is a regular DS game and will work on any model. There are also some enhancements which only work on DSi, and 3DS, like WPA decryption and camera functions.
I say 3ds for the win 3ds has a camera and full 3d graffiti gravediggers
the Nintendo that has the camera is the Nintendo 3ds or Nintendo dsi