motion tracking and still footage

I wanted to ask if it is possible to track a still footage (not a single image) a video and add a virtual object,and also is it possible to add a virtual object behind a person in a real footage for example like a person is standing and there is a cube behind it Half of it being covered by the person in the footage if so then how is it achieved ?

I wanted to ask if it is possible to track a still footage (not a single image) a video and add a virtual object
If it’s a stable shot, you may use the addon called “BLAM!”, which will help align the virtual camera and approximate its focal length. If the shot is rather shaky but lacks perspective shift, you may use a tripod solve (available in the latest test build). This will not align the camera, but will instead extract its rotation.

is it possible to add a virtual object behind a person in a real footage
Yes, by using rotoscoping.

There’s a bunch of tutorials on these subjects, just do a search.