Interviewing for FT Spots during IB Summer Internship

I have a couple of questions regarding interviewing for full-time IB M&A spots while being an IB M&A summer analyst:

1) How do you take time off for longer interviews / assessment centres? Work from home helps but the combination of long hours and unpredictability of the job can make it difficult to plan anything, especially at short notice.

2) How do you communicate it to a recruiter that you cannot attend an interview on the interview day, providing you have a fire at your job? Would be good not to get blacklisted.

3) When do you find time to prepare for interviews? E.g. you get an interview on Monday and your interview is on Wednesday and the interview is for a specific sector team you do not know much / enough about. All I can think of is: 

a) Pulling an all-nighter. I have done this before, but doing an all-nighter diminishes my interview performance.

b) Delaying an interview. I have done this before as well but not sure how well it was taken given that it probably did not leave a good impression on a recruiter.

4) Any advice how to make sure that the team does not find out about it? It is a very small world and people talk.

5) Any other advice?

Thank you pals!

P.S. I am done with my studies, and I do not want to go through a normal graduate process which would make me wait for a one year until I could start working.