I am wondering what happens if you go over the allowed credit limit for 1st year courses?

Do you mean if you take over the 48 units? If so, they don't count towards your academic record.

Essentially though, you shouldn't really go over the limit. Because it provides you with a chance for a full course load in first year with level I courses and 1 full year course for each of 2nd, 3rd, and 4th years. And most of them would have to be electives, since you do have to satisfy the requirements of your program.