The person who filmed it, unless they filmed something they did not have the rights to film, owns the rights to the film.
no
if you filmed people yes, if you filmed the street, and people happened to walk by, no. It’s a fine difference but very important.
yes. If they expected privacy and it was violated they can try to sue the producer of the film and anyone who distributed it. They can easily contact, say youtube and have the video removed. For actual legal proceedings, I can’t exactly give advice here (or anywhere really).