Yes; many people have done it. Indeed, most serious cruising GP14 sailors regard this as an essential part of the rig.
I would refer you to the paper on reefing systems in the Members’ Library on this site, which should answer all your questions.
Using your sail which is older than the best (or did you mean older than the rest?) as a reefing sail: yes, fine, but only if it is in good enough condition, and if it will set reasonably flat when reefed.
Oliver
(Erstwhile Cruising Rep; and a.k.a. “He who reefs”)