Correctness of subordinate clauses?

Hi. Please help. I think the underlined parts are subordinate clauses - not sure, though. Are the following correct? I think the first three are correct, but I am not sure about the fourth sentence. Thank you in advance.

1. Jim was playing basketball with John, with whom Joe studied for the next week's exam yesterday.

2. Jim was with a group of friends, some of whom Joe saw playing basketball with his friend John yesterday.

3. Jim played basketball with three people, two of whom he became best friends with.

4. Jim studied mainly with three friends all through high school, one of whom became one of his biggest benefactors.