You can undo your recent actions, redo them, or revert the changes you've made to a photo all at once.
Undo the last action: Tap or two-finger tap the screen. Tap multiple times to undo up to 200 of your recent actions.
Redo the last action: Touch and hold , then tap Redo, or three-finger tap the screen. Repeat that if you'd like to redo more than one action.
Revert changes: You can also tap to restore all the changes you've made to a photo in the current and any of the previous editing sessions.
Cancel changes and quit: If you'd like to quit the photo without saving any of the edits you've made, tap Cancel in the top-left corner of the screen and choose Discard Changes.