@AmyM62 You may not need to access the beta instance to recover your students' work on the exam.  Since you state that the exam isn't assigned to them, you most likely can recover their work by editing the exam and assigning it to "Everyone".  Even if the content of a quiz is overwritten by an import, any existing submissions will not be overwritten, so you should be able to those submissions for the exam still--though grading might be off if the points changed as a result of the quiz being overwritten.  Secondly, you may not have overwritten the original exam but instead created a duplicate version with the same name.  Canvas doesn't identify content by its name, but by the Canvas assigned id for the item, and it would only overwrite a quiz if the quiz had been imported into the course from another Canvas course previously and then reimported from the same course again.