you can make animation go forwards and backwards.

  1. create the animation
  2. click and drag on the timeline to select all the frames ( do NOT click first and THEN click-and drag, you'll move your frames, just click and drag all at once)
  3. right click COPY FRAMES
  4. click on the next empty frame
  5. right click PASTE FRAMES
  6. click away to deselect
  7. click and drag on the timeline to select all the copied frames
  8. right click and select REVERSE FRAMES