My thoughts

1) From the information you provided, the Jr. FA and FA may belong to different Finance groups/ hiring managers. It does not hurt to apply for the FA. You have nothing to lose at this point.

2) The recruiter did the initial phone screen few weeks ago and did not get back to you on the next step. Did you send a thank you note to the recruiter after the interview? It may not be a bad news. You can send the recruiter a note asking if any decision has been made and express your interest and why you think it is a good fit again. I don't think you should ask for a volunteer opportunity though. It sounds weird and not a common practice. Volunteer jobs are more related to school, church or other non profit org. It is a good idea to find a volunteer role and get some experience when you are at school.

3) Alumni is one way of networking, though, in your case it probably won't help much.

Suggest you prepare well next time for the interview. There are some common questions you can find online. Good luck!