As educators, we will always update the content of our course, and it will be helpful if there is an option whether to apply the changes to a specific class instead apply to all current and previous classes. For example, for the current semester, I have updated a new assignment for my student and deleted the previous assignment. However, this change is also applied to my previous classes.  This will also help in terms of audit... and in the case of my institution, students can always request for their marks to be reviewed after they received their grades. Therefore there should be options to access our previous classes (and students' submissions) as to how it was prepared previously. This will also allow the educators to customize the content according to students in each class.