If someone made revisions to your PowerPoint presentation but neglected to tell you what they changed, you can use the Compare feature on the Review tab.
Although it may give you pause, go ahead and click on the Merge button, Compare dialog box, once you’ve selected the revised presentation. Your original presentation should be open. It will show you what was added, deleted or changed in markup notation. Similar to Word, it gives you the opportunity to accept or reject changes one by one, by the slide or all at once after you’ve reviewed them.
If you want all three versions, save the merged copy under another name.