In the Hapkido I learned, we had a back kick such as the second you described. It was normally taught as a kick to the neck/head, almost like a mule kick. It can of course, also be used to strike a knee, groin, solar plexus, or head/neck.
We also had two spinning hook kicks. One to the waist area, the other to the opponent's ankle. Inasmuch as they are spinning kicks, they tend to be very fast and powerfull. I doubt the waist kick could be caught, I am quite sure the ankle kick could not be since it is so unexpected, and would require the opponent to reach down awkwardly to try to catch it. The spin kick is most effective with proper technique. Stepping forward to on the toe and pushing off the now back leg into a kick is powerful. However, stepping just forward of the lead foot, with the back foot, then pivoting using both toes and legs, produces much faster spin. That is a dangerous kick to try and grab at the waist. At the ankle, probably impossible. The ankle of the opponent's plant foot is the target of your heel. That will break the opponent's ankle rendering him unable to fight. For the ankle kick, you should fall forward on both hands, putting all concentration and power into the kick, none into balance.