You can go to college, but you must meet certain requirements. You can also take classes when you are admitted to Zhejiang University. Universities generally have no audited units. If you especially want to go to college to attend classes, you can go directly to the classroom. Generally, teachers will not care about you, especially when there are many people. But only if you listen carefully and don't disturb the class order. As long as it doesn't affect the normal class of teachers and students, most students sit in the back and ask if they live on campus like normal students, that is, they don't have a diploma. Answer me, for example, that is to say, people in society can also attend classes for free. They need to buy their own textbooks, no exams, no student status, and no dormitory allocated by the school, that is, they don't have to pay tuition.