View Concluded/Inactive users in the Gradebook
You can always access "old" courses and view all student information in those courses. No grade information, or assignment submission, is removed from the course, the students are however moved to an inactive (when dropped) or concluded (when a grade is issued) status.
You can view this information (grades & assignment submissions), but you cannot edit or change any information if the course has been fully concluded. Courses are moved to concluded status either once grades for all students have been recorded in self-service, or 6 weeks into the next term.
Below are the Canvas guides that explain how to access previous courses and view grades/assignment submissions for inactive and/or concluded students.