There are two issues with generic lens hoods.
First, the depth of the hood must be coordinated with the focal length of your lens. A 55-250mm zoom is going to be harder to match - a hood that either has a large enough diameter, or else is shallow enough to not vignette at the wide end of the...
No.
The objective of prom photos is to show people. If anything, you want to reduce contrast in order to create more flattering images of those people.
Using a polarizer (circular or linear) would be a mistake.