Film Festivals - Who Controls a Final Product?

i would imagine that the whole purpose of going to a sunday or two, italiarid or two, whatever is south by, southwest especially, is a great buzz and a market for your film that does not yet have a distributor. But definitely, i guess it's also a question of, ah, when who controls a final finished product? And then what woes te other show thati'm watching that's on right now on hp mx. Oh, somebody somewhere the bridget vort show, which is really cool.