Task 3
Preview the Extraction by applying the effect with the Preview Button top left. Again if the result is not as desired then you can Reset with the Button above Note: not in all versions. Or Ctrl + Z to Undo

Making adjustments
Any areas that are missing or any artefact not removed can be manually altered using the adjustment tools.
The Clean Up Tool (C) or the Edge Touchup Tool (T) both use the Alt Key to Moderate (reverse) the action.
This is as much an art as a science and the results are also depend on the subject. Experimentation is the key. Look in detail at the artwork and observe the many variation and the applied results.