When I did it the lecturer gave us a list of which topics the essay could be on and I just had a skim through the theories. That said, I winged multiple choice and it was lols.
You can actually pull off a white blazer with black pants and black patent leather shoes. However, I would lean on the side of caution given that it's a formal and white blazers are usually reserved for when it's hot i.e. summer. If the formal is specifically mentioned as being black tie, don't...