Scrape some of the back of a hinge, if it's hard to tell. If you look at the end of the hinge, where the knuckle ends, you can usu. see by looking - a brass hinge may well have machining marks, and the pin should be almost indistinguishable from the metal of the hinge. "Brass plated" hinges are generally more poorly made and are "looser".
Ask the man that made the window :~).
Primer, undercoat, gloss (coats) is normal.
Yup - however, maintenance should mean that it's not needed!
The problem with beading is that it is more prone to leaks and rot. It should be secured with non-rusting pins to prevent rust bleed through the paint. I like putty!
J.B.