Let's start with the first split in the air and then a cross kick. In Taekwondo, cheating in the air is called cheating jump. First, you can open the cross on the ground, and then practice belly jumping. Finally, you can spread your legs to both sides in the air when you jump in your belly. Legs must be straight, and of course you can run up and take off.

After you practice this movement, you can divide your knees in the air and recover your legs. When one of your legs hasn't landed, turn around and whip, and the cross kick will come out. But you must have three things first, otherwise you know how to practice but you are not competent. The height in the air, the strength of the waist and abdomen, and the control ability of the body in the air. It is enough to practice run-up and belly jump at the height of flight. I don't need to say the strength of the waist and abdomen. As for the control ability of the body in the air, you can control it slowly by practicing this whole set of movements.

As for the 720 fly kick, you mean the 720 spin kick.

This is a little big for you. Kicking in the air can be explained by words, but the spinning stunt is too complicated.

I can only tell you, practice single whirlwind kick and backspin first. Let's do the stunt again.