Looking at the Windows 10 "Photos" app, I cannot find a way to make it show the picture in fullscreen without running a slideshow. I installed the old Photo Gallery program, and then I realized that Windows 7 did not support this either! I either want a way to play a slideshow where it does not change pictures until I press a key, or I want a picture viewer that is capable of fullscreen viewing or a slideshow like I mentioned earlier. Thank you for your suggestions!
Irfanview is a great photo viewer. It will show individual photos, it has full screen display or part screen with menus and toolbars. It has 'next' and 'previous' photo commands in both modes. It can do slide shows.
It works fine on Windows 10 and I have used it on several other versions of Windows.
Xnview is also really nice and does what you want. Personally, I like it better than Irfanview, but that's probably a matter of taste.