1st, eww... not even close to realism... needs more relax, needs more intention to the jumps. Try not using your hands so much. Cause tricks are landed only on the feet. 4/10.
2nd, same stuff. Needs more relax, and less waiting before making the jump. 6/10.
3rd, btw, if you did not notice, you're not doing any backflip out there, thing you do is called the back layout. Need tons of work with the movement. 6/10.
4th, way to fucking much gravity. 2nd jump was very bad... 3/10.
All in all, 19/40 ~ 4,75/10.
Work on the movements.