To flip your graphic, first, click to select it. Next, click on the Flip icons in the upper menu. You can choose to flip it vertically (top/bottom) or horizontally (left/right).
Undo individual actions by using the Undo/Redo buttons at the menu toolbar on top. Or use keyboard shortcuts CTRL-Z to undo and CTRL-Y to redo.
To reset to initial orientation, just double click on the rotate handler (the dot at the top). Resetting will return a graphic to its original size and rotation.