Cod warzone? Ps4?

I would like to play cod warzone but don't want to download mw but only warzone because I already own Cold War how can I only select warzone

Not at all. You can just download everything and then delete the multiplayer files.

Yes, that is possible. Simply search for Warzone as a package in the store. Alternatively, I think you can also select Warzone via the selection in the start screen. You can see what happens, it might throw you into the store.