USA Volleyball. This one is pretty easy.
A player receives the serve with an ugly-looking double contact, but there is no call made. Volleyball slide tips and techniques for spiking.
This is one of my favorite serve receive drills because it's fun, competitive. The R1 is in charge of the match.
Everyone seems to be referencing the old rules or regional rules but in international FIVB Volleyball double hit would only be called if you make 2 attempts at playing the ball, so yes it's allowed to slip through your fingers and bounce of but in the end it's up to the ref, the kicking example is slightly more controversial because you may have planned to create that bouncing impact and in that case it's the refs decision.
Serve receive drill that teaches anticipation and forces servers to take chances. However, the block and the first team hit are exceptions to this. R1 may prefer the down ref to whistle and make the call on obvious back row attacks and obvious back row blocks.
If the player takes support from the net.