final cut pro cut out object

It can be done, probably. It depends on the object. It’s basically animation, which is tedious. Plugins can help a lot. Check out SliceX and TrackX from CoreMelt.

The background is the bottom layer. The green screen is the middle layer. Another copy of the background goes on to. You can use draw mask to cut out the object you want in front. You invert the mask do it cuts out everything except the object. Then you have to animate it. Adding keyframes as it moves across the screen.

You can technically, chromakey out any color, not just green or blue. I do it all the time:

https://youtu.be/-H91k-mrhZs

I just keyed the Eiffel Tower, then inverted the mask (and: no keyframes). It's all basically the same color. I just did not use the Keyer to accomplish it (although I probably could have.) The Keyer in FCPX has a manual "mode" and it is, with a good deal of effort, capable of keying out colors not green or blue.

There are some plugins available that make the job ("worlds") easier than using the Keyer in FCPX, but you won't find out about them here. For 1) according to the rules, I can't tell you; and 2) nobody else knows or cares the plugins exist. If it ain't on FxFactory... it doesn't exist! [Man! I'm getting cranky in my old age.]