practically speaking, you can succeed in cloning a system image to another disk, and with a little luck and prep work, you can get it to boot, without any activation problems. (I spoke about this in another thread.)
and then, if you unplug the new disk, you can reinstall on the old disk.
but... if you unplug the old disk and try to reinstall on the new disk where you cloned your system image, that's where you get into trouble. It will install, but in the end, it will not activate.