The operative phrase being “no simple answer.” Each college is free to determine definitions and, where allowed by law, determine what bump, if any, any of the attributes will be given.
For the OP, these questions on URM and first gen need to be filed under “it is what it is.” There is no box on any application that says “Check here if you are first gen/URM/legacy, etc…” The applicant simply fills out the biographical data for themselves and the parents, including their education, and each college will decide what (if anything) it will do with that information.