WHY does my kitten do this?

yes they are absolutely normal things for cats to do. the kneading is something they do to show affection usually if they have been taken away from their mother too early and sometimes they just do it because its comforting. mine will actually knead my blanket when he wants attention. the hopping and rolling over may be her way of saying she wants something like attention or food. try petting her face and shoulders instead of her tummy and see how she reacts. if she still gets up and walks away follow her and see where she takes you.