Q: Can students delete the submitted file from the wrong Assessment Activity?
A: Yes, they can. If they submitted an assignment to the wrong Assessment Activity, you can simply remove the file by themselves. Click Edit submission, remove all the uploaded file and message on the description box (if any). After that, click save. The Edit submission button will be changed back to Submit.
On Assessment list, the button will be changed back to Submit as well as the status will be shown as Not submitted.