Is it possible to undo the carpet flooring above wooden floor?
Sure, just pull up the carpet. At that point, it depends on the condition of the wood floor. If it was in very poor condition and carpeting was installed to cover it up, you may have a big job of refinishing or replacing it. Otherwise, if the wood floor is in good condition, it's mostly a matter of using some color-matched wood putty to patch the holes made by the carpet tack strips' fasteners around the perimeter of the carpeted rooms.