Can new activities added in a course be tagged and reset for all enrolled employee?

Summary: If an employee has completed / not started / in-progress trainings, what if new activities are added in the trainings, what will happen to employee's current trainings? how can that be added to employees if we have to?

Content (required):

Version (include the version you are using, if applicable):

Code Snippet (add any code snippets that support your topic, if applicable):