I think 3th frame could be better. When he starts his jump with only one leg, it means 50% jumping power instead of 100%.
You could check this backflip for reference. He's doing backflips around 3:50: https://www.youtube.com/watch?v=Q_p4dybt94c . He is doing a backflip with legs together, but the start should be the same in both variations. Knees bent about 75 degrees, back not completely straight but diagonal. This allows for the most powerful jump.
Other than that, way to go
You could check this backflip for reference. He's doing backflips around 3:50: https://www.youtube.com/watch?v=Q_p4dybt94c . He is doing a backflip with legs together, but the start should be the same in both variations. Knees bent about 75 degrees, back not completely straight but diagonal. This allows for the most powerful jump.
Other than that, way to go
