I'm sure it will vary on your program but for mine:
1) Anywhere from 1-3 days per week, usually 2 for me. Each clinical lasts either 6, 8, or 12 hours. I truly depends on the location and how they schedule you. I might have 2 days in a week where I go to clinicals for 8 hours each and then the next week I might have just 1 day but for 12 hours. We also have simulation labs scattered throughout the semester where we are in the campus virtual hospital for 3-6 hours at a time. Your program could be completely different though.
2) Definitely no. You do what your instructor/assigned nurse tells you to do. And this includes cleaning up people and you're really not going to be able to avoid that one...
3) We get one 30 minute lunch break if we work 6 or more hours. Sometimes we can sit for 5 minutes with some water if there is a calm moment but I wouldn't expect it. We do some sitting when we are charting or looking at the computer medical records. Do you have some sort of doctor's note?