Hi Peter,
I've used it in Desktop mode, but not Mobile mode, so I can imagine there might be issues there.
As to selecting which camera to use - I'm not 100% sure about that. I'd have to try on a device with 2 cameras I guess.
We are using it successfully in one of our kiosk-type apps, but the camera in that case is an external USB one, so doesn't really speak to any of your questions...
Cheers
Bruce