You can flip an image both vertically and horizontally in Edit mode.
You can save your settings as a preset for future use.
To Flip an Image:
Click Reset to clear your changes and reset to default settings. If you saved your changes, you cannot reset your settings. If you want to discard only the Edit settings, select File | Restore to Developed.
You can use the Edit Brush to paint this effect onto specific areas of your image.
You can use the Gradient tool to transition this effect across specific areas of your image.