Question

"if jerome won't have a relationship with someone who lives in his dormitory, which he jokingly refers to as "dorm-cest," he is practicing the rule known as:"

Answer 1

I believe the answer is: Exogamy

Exogamy refers to The practice of marrying only the person that IS NOT a member of their community.
People who adopt exogamy tend to seek their life partners from outside the city or even the country where they grew up.