I'm not a Purdue student, but I'm going to encourage you to drastically reframe your current paradigm about 4th year. 4th year is not a gauntlet to be run, where gloating clinicians ask the impossible questions specifically to have an excuse to fail you. Nor is it a year where the program runs you into the ground to the point of you being a danger to patients due to sleep deprivation.
4th year is your chance to be a doctor while still under the supervision of actual doctors, and some of that is dependent on what you make of it. For example, I'm on one of my program's busiest and "hardest" rotations right now (small animal surgery), and the amount of involvement students get with the decision-making for their patients is really dependent on what they put into it. For me, I really want to get as much out of 4th year as I can, so instead of just asking the clinician what they want to do, I make my own treatment plan and come to rounds ready to discuss it, and learn what I could modify in it to best fit that patient that day. I've gotten to do things in surgery because I showed interest and took initiative to help out. Of course you're going to be asked questions, but you're not being asked questions with the intent of making you look/feel stupid, or to find an excuse to fail you - it's to make you think critically about that case. Don't be afraid to be wrong or to say you don't know - but rather than ending with "I don't know," take the approach of "I don't know, but I will look that up and get back to you."
There is always that clinician who is an unreasonable curmudgeon, and sometimes you'll get lectured on things that were out of your control/not your fault, but that's the minority.
Some rotations will have long days and on-call - most of my days last week were >12 hours, but just as many won't. You absolutely will not be working "16-20 hour days with *maybe* one day off per week" - that's a hazard to patient care. Remember that your program wants you guys to succeed both during 4th year and as graduated doctors; it does them no good (and doesn't get them as many alumni donations, to be frank) to intentionally be failing students.
Come in, have a good attitude about what you're learning, take initiative in preparing for your cases each day, and check in with the clinicians halfway through your rotation to see how you're doing and what they'd like you to do better; that way you won't feel blindsided. You'll be fine.