Have Spider-Man and Flash ever fought against each other?
If so, who won (and how)?
I can't find or remember any such conflict in licensed media. As mentioned above, there have been crossovers, but these didn't involve direct conflict between these two characters. In DC vs Marvel Comics, The (Wally West with access to The Speed Force) Flash beat Quicksilver, (Ben Reilly) Spider-man beat (Kon-El / Connor Kent) Superboy.