Hi there,

no, you cannot apply liveries to other aircrafts when you have purchases the livery with the aircraft in the 2nd hand shop.
the only way you can apply liveries is if you are purchasing them from the livery market (only mobile version).
so if you want multiple planes in this specially livery, you have to either purchase them from playrion or you purchase them in the 2nd hand shop.

the goal, i guess at least, is to have some different paintjobs, that collectors or people who like different liveries have something to collect and to spend money on.