If i shared food with someone who had mono when they were 2, will i get mono?

Unlikely: While one has antibodies for life after being exposed to the virus that causes mono. The virus should no longer be causing a problem.

Don't worry about it: Mono is caused by ebv virus, and a great many people already have the virus by the time they reach adulthood. Kids who catch ebv when young often get a milder, shorter illness (they don't remember ever having mono). There is no way to tell if one will get mono from sharing a single meal, 5 meals, or 50 meals. Ebv is generally considered a part of life. People don't spend time trying to avoid it.