If you publish a content item from Presenter, Quizmaker or Engage, you may be prompted to overwrite an existing content item. If you say Yes, the original content item will no longer be available for viewing. It will be replaced by the new content item you publish to your account.
You will still be able to run reports on the older versions of the content item. When running a report, you will be given an option to specify the version of the content item you wish to run a report on.