Yes, it will fit any Sony e mount body, either full frame (a7..., a9...), or aps-c (like a6500, etc) 

I trued it on my old camera a Panasonic dmc-fs5 and it didn't work. 

yes, i had no problems with infinity focus with this adapter. the only FD mount lens i use anymore with my sony is a vivitar 20mm, and i pretty much only shoot infinity focus with it. 

The adapter clicks on the lens. It has a small dark gray colored lever (not the white plastic tab to change aperture), level to the outer edge of the bottom ring accessible when removed from the camera, grab the whole adapter with your left hand and push the lever in with your thumb, and while pushing, rotate the lens with your right hand to remove it. You need to push in that lever to unlock the lens. 

I agree with eddie - I have not really needed to support the 15 pounds that it should handle. With my camera with battery grip, 135mm lens and hanging my camera bag with extra body and 3 other lenses from the hook there was no visible deflection on the tripod legs and made it super stable. Any DSLR with standard screw mount should work without problem. My canon 70D had no problems.