To reset all changes made to a slide in Microsoft PowerPoint 2013, you can follow these steps:

1. Open the PowerPoint presentation that contains the slide you want to reset.
2. Navigate to the slide you wish to reset by selecting it in the left-hand pane or using the slide navigation buttons at the bottom of the screen.
3. Once you have selected the slide, go to the “Home” tab in the PowerPoint ribbon at the top of the screen.
4. In the “Home” tab, locate the “Slides” group, and click on the “Reset” button. It is represented by an icon with a curved arrow.
5. A drop-down menu will appear with two options: “Reset Slide” and “Reset Layout.” Choose “Reset Slide” to reset the entire slide and discard all changes made to it.
6. PowerPoint will prompt you with a confirmation dialog box asking if you want to reset the slide. Click on the “Reset” button to proceed.
7. The slide will be reverted to its original state, undoing any modifications or changes that were made to it.

Note: This process will reset the entire slide, including its content, formatting, and layout. Make sure to save your presentation before resetting the slide if you want to keep a backup of the changes made.