Why not emulate just about every other text editing software and add shortcut icons for Undo and Redo at the top of the editing window? I went years not even knowing that this feature exists in Evernote! I can never remember the keyboard shortcut for Undo and I can never find it in Evernote's help, so I have to do a Google search. This wastes a lot of time.
This answer was non-responsive. The OP asked how to delete a photo ON AN IPHONE. The answer was for how to delete a photo on a PC. I also need the answer to this question.