When studying from past exams you should be mindful of the fact that, while the CS70 syllabus has been quite stable for many years, the detailed content does vary slightly and you may find some topics in the exams that were not covered this semester: you may safely ignore these.
Similarly, the precise coverage of various midterms may vary from semester to semester. Notably, there is only one midterm this semester where as previous semesters had two so make sure to look through previous Midterm 2’s while studying for this semester’s midterm.
Ultimately it is this semester’s lectures, notes, sections and homework that determine what you are expected to know for this semester’s course and are the best resource to study for the exams.