Cloning or Copying a ROON ROCK NUC

If that’s all you mean by ‘clone’ then no problem. Roon never touches music files, it only reads the files.

Yes, many people do, but only one can be active at any one time.

No problem, as long as you haven’t set a static IP inside ROCK…
I forget whether ROCK lets one set a static IP, but one should never do that anyway.