Can't really work on speed. You either have it or you don't. Otherwise, there would be no slow fighters.
Not true. First there's footwork drills you can do to increase the speed for getting your body set to throw a shot and there reaction time drills to do as well that can decrease your reaction time for pulling the trigger
I don't mean reaction times or timing. I'm talking about speed of punches. Name me some fighters who were slow and noticeably increased their speed through training.