Can Guests Delete Photos From the Gallery?

Yes, guests can only delete photos/videos that they have uploaded. 

Once you are in the gallery, select any of your own photos that you wish to delete. In the bottom-right corner, you'll see the ''More'' option then you can select Delete. This will remove the photo from the gallery permanently.

Guests do not have the ability to delete content uploaded by others - only the host has the ability to remove any and all content if desired.