Can a 15 year old have a job or part time job?

Yes can do it

if the employer will hire him

the chances are EXTREMELY LOW !!! i myself have been looking ALL DAY and everything i find requires being 16 years old AND I HATE IT !!!!!!!

In the USA they can

There are limits but yes

Yes but it's hard to find one. Try local jobs in your community. Most placed don't hire until at least 16

Part time, yes, but only balanced with school, which is your full time commitment.

yes, absolutely.