I've heard that the Phantom 3 is programmable.  Is there an SDK (Software Development Kit) available?  Does the programming interface allow general-purpose programming in a high-leve language such as C, or is does it simply allow the programmer to set options and paramters in a meta-language?  

I believe it allows the dev access to a set of API's.. I'm no programmer so I will direct you to here http://dev.dji.com/en   - have a read

I got a Phantom 3 Professional, and I try using visual studio control aircraft and camera
but seem not work, I install drive and micro USB link with aircraft and pc(win7) com8,
did that link with aircraft not with remote control, right?
I try example (uart/usb), they doesn’t work..