Part of the "fun" of the assignment is that the requirements aren't exactly consistant throughout the exercise. Therefore, part of what you're going to have to do as the architect is make assumptions on what the customer (FBN) wants and how best to design your solution.
Whatever you decide these statements mean, and therefore what's required, is going to affect how you design the solution. Just think it through, think about how the different definitions for 'leg of a flight' in the various contexts, and go from there (while documenting your assumptions).
A 'lay over', if you're asking for definitions, is a period of time between flights before a transfer at an intermediate airport while travelling to your destination.
I know that's not terribly much help, but I'm also trying not to affect how you design your solution or give "answers" that bias the
test.