The correct answer to the Half Twisting Leap Frog quiz is the skill is first Legal in Level 4 as performed in the video. During the leap frog the top person goes inverted. In Level 2 inversions may only be performed going from ground level to a non-inverted position. In Level 3 inversions are restricted to shoulder level, unless meeting the criteria for a suspended roll. In Level 4 inversions are allowed up to extended level.
The half twisting leap frog in the video below, without the top person going inverted during the transition, would be allowed in Level 2.
This ruling and explanation are based on the 2016-17 version of the rules dated August 31, 2016.