I majored in computer science, 12 majoring in mathematics in Dalian University of Technology. Mathematics majors don't take math 123, but we take math major courses: mathematical analysis and advanced algebra. The content of mathematical analysis is similar to that of advanced mathematics, but it is more professional, deeper and more difficult. The content of advanced algebra is similar to that of linear algebra, but it is definitely more difficult. Each school of the postgraduate entrance examination course for mathematics majors has independent propositions, but they are both two courses with high scores, mainly based on proof questions. The difficulty is certainly there, but it will never exceed the content of undergraduate study.

I'll give you a test question and solution for the postgraduate entrance examination of mathematical analysis in Peking University for your reference.