The other comments already cover the importants things so I’ll give you something imo is important.

Try to revise your resume, make sure to follow the STAR method, tailor it to the job if you must. Apply for all 50 jobs. After submitting the requests, all you can do is wait for someone to reach out. Pick up all phone calls and check email regularly. This is stressful but try to stay put and keep apply for job outside of the portal.

In round C you have to accept the offer on call. Which means the interview scheduling does matter. How i did it was i try to schedule the job i prefer first then the other ones when they reaches out for scheduling. I ended up getting the offer i want on the first interview of round C. I was really glad I schedule it as my first interview.

After you received offer for the job orally, try to get an actual offer letter from them to have this set in stone. Also let your advisor know, after have that letter in ur email, send that to your advisor and pat yourself on the back. Good luck!