how can i tell to my application made by unity to disable my GPU and force to work with CPU only ?? and how can i make sure, it is using only cpu , not gpu ??

i made simple redcube which can constantly rotate by unity…
unity profiler can tell me about rendering on GPU and CPU as well,
But my question is how can i disable my GPU from unity and force to work with cpu only , and how will i check it for the same ?

Look at the standalone player command line arguments here: Unity - Manual: Command line arguments

Check -batchmode and -nographics.

You need the GPU to render the image and CPU to compute the physics so you need both to run a Unity app.