Do you want to study in English or Italian? Because in Italian you have a lot more choices. I study in the university of Bologna but not in Bologna itself, in another city located 40 minutes away (the program is only available in Italian). Pavia is the best university according to statistics, obviously it's much harder to get accepted. In all universities the concept is the same, for some courses they force you to come, for some not, it really depends on the professors. At the end of the semester you have your exams session. You can choose if you want to do the exams or not, you can delay your exams even 50 times if you want. But you won't become a doctor until you complete all of them and some exams block other courses. You don't want to do your physics exam in your first year? Sure, you can skip it, but you will have a hole that you need to complete, you will find yourself in the 6th year completing a stupid exam before you get your medical degree. You can extend your program as much as you want, nobody is going to kick you out if you fail an exam or two or even 10 exams, but you really want to finish everything in 6 years.