No. Footage must be shot on a tripod and have no camera movement. Any subject or subjects that you want to remove from the scene must be in motion.

We recommend only using 1-2 monitors when editing with FCPX Removal.

To accomplish this effect create a duplicate of your clip and place it directly on top of your footage and hide it for the moment by selecting it and pressing V on your keyboard. On the bottom clip apply the FCPX Removal effect and run the effect so you have all moving subjects removed from your clip.
You should now have a base to bring one subject back into the scene.Now select the top copy of the clip that you hid previously and press V to unhide it. Apply a draw mask effect on your top clip and create a mask around your subject you want to bring back into the scene. Next key frame the mask on each frame making sure it only surrounds your subject. Now you should have all other subjects removed from your scene with the exception of your main subject.

No, this plugin can not remove entire backgrounds. It can only remove subjects in motion that the background can be seen behind for at least one frame while the subject is moving.

No. In order for this plugin to work each section of your background must be clearly visible for at least one frame of the clip. The subject must be in motion and have enough movement to reveal the background behind it. If the subject is still, the plugin cannot see the background behind that subject that is needed to replace it.