Presumptuous straw man…
"Can God change the past?"
"No…then it is not God"
Easy to construct specious word-play arguments when you begin with this kind of idiocy. Ascribing attributes to God is fun, I know…but there is nothing to say that God must possess whatever attributes you want to ascribe to Him for your silly arguments.
God cannot do anything. He exists. Move along and stop pretending to be smart, because you're a fool.