God is formless and he assumes a form, say. Then that body is bound by time, space and causation. And anything bound has to change. But god is constant. Then are incarnations true? Then where are all the incarnations so claimed? Can an idol be called god?
Also how can god be with and without form? The idea that he is both with and without form is false. Because when the form dies a part of god dies. But god has no part, he is whole, changeless.