My hubby's IVs last year kinda went like this.
Usually a program has a pre-interview dinner, its the night before, not mandatory but its a good opp to mix with the residents, they can put in a good word for you.
Usually IV day is from about 7:30-9am till maybe 3-4pm. Of course you wont be interviewed throughout, but some progs have 3-5 short interviews with diff profs/PDs/chief residents etc, with each lasting 15-20mins. There is usually a lunch period, tour time etc.
No sometimes everyone is interviewed at the same time, because there are diff ppl interviewing applicants.
Pls dont be discussing your scores and app with others on IV day, smile at everyone and be courteous. Be ready to discuss your app, know everything you put in there, know your PS, be ready to tell your story, strengths, weaknesses, diff challenge you've ever handled, future goals, medical case you've handled, anything is fair game. IV is a time to sell yourself, but its also a time to be honest and really be yourself, time for you to ask reasonable questions. If you cant speak English well, or if English isnt your 1st language, pls practice really hard, because you may have a hard time explaining your answer and easily lose out on a great spot.