Lennart: In the Failure diagrams, white is not really living in ko, because after white at a1, black takes the ko with b1, white makes a ko-threat somewhere, black answers, white takes the ko by playing a1, then black can take the other ko by playing c2, white has to make a ko-threat that black answers, and so on. Black will never have to play externally to win the ko, which means that white is really totally dead in the failure diagrams. Please tell me if my analysis has any error. Thank you.
Bill: Yes, it is a double ko death. :-) I have added the diagrams to show that.
unkx80: Thanks, and a minor WME + correction to Failure 1 diagram.