Is the word "unsetup" valid in English?
Normally the opposite of a set-up is a tear-down.
While creating a new word is perfectly OK, and quite common in technology in particular, unsetup is not an existing word in current common use.
Unsetup as an adjective, meaning 'not (yet) assembled', would be comprehensible. You appear to want a verb the opposite of set up, and the problem there is that it has no opposite in normal parlance, so there is no word for it. Similarly, there is an adjective uncreated, but no word *uncreate (though destroy does the job most of the time).