[Serious] Could an omnipotent and omniscient god prove that he was God?

[Objectivist]

It was aimed to show why the notion of a god creating it is philosophically incoherent.  It violates facts about the nature of the universe that are in evidence, namely the axioms and the primacy of existence.

So it would seem. However that approach risks riefying an abstract principle. Does it not?

At the same, time you are presenting this axiom as a brute fact.. But it is curious to me that you do it in the same way I,writing as a thiest, reason for a Necessary Being, i.e that which must exist for anything to exist at all. How about Being-Itself? Would you not say that Being-Itself must exist logically prior to any particular being, i.e. being-as-such? And if so, would not the concept represented by 'Existence exists' be identical some being, call it God, whose very essense is to exist.

At the same time, we would both agree the principle of non-contadiction is an absolute, but only as an abstract proposition.  The PNC has no power in itself. The PNC is mind's perception of an effect of a divine logically prior cause, the power behind the proposition.

Abstractions are based on facts.  They are not just some made up thing that bears no resemblance to reality.  So no, the axiom of existence is not the same as saying there's a god which is necessary for everything to exist.  No, it says everything already exists and there's no need for a god to create it.  

You say that the law of identity and the law of non-contradiction are absolutes and they are even though they are abstract principles because the facts on which these two abstractions are based on are absolutes.  Every fact is absolute and necessary.  To exist is to be necessary.  

Your formulation, that some supernatural being is necessary for existence to exist treats existence as a derivative or contingent fact instead of an absolute which all facts are contingent on and this is why the notion of god contradicts everything that we know to be true at the most fundamental level possible.  If you are pointing to something that exists as an explanation for existence then you haven't explained existence.  You are just appealing to the very thing you want to explain in order to explain it.  Asking what caused existence to exist is like asking what's north of the north pole or what existed before everything existed.  There was no before the universe if you define it correctly as the sum total of what exists.  The universe doesn't exist as such,  It's a concept.   

Your brain can only deal with about 7 different concretes at a time.  That's its limit.  That's why really long sentences are frustrating, they are overloading your mind with too many things to pay attention to.  In order to live we have to deal with an enormous number of concretes on a daily basis.  Concepts or abstractions make us able to deal with an enormous number of concretes by turning them into one mental equivalent.  Each and every concept subsumes an unlimited number of units or similar things.  The concept of man subsumes every man that has ever existed, will ever exist, and that exists now.  It turns all that into one mental unit. The units of the concept universe are everything that exists, all their attributes, their actions, their relationships including their motion relative to each other also known as time.  Everything.  So to say who created it all is nonsensical.    

Now, this whole notion of necessary vs. contingent facts comes from a false dichotomy called the analytic-synthetic dichotomy which is the result of a faulty theory of concepts.  Christians and other theists fall prey to this false dichotomy because they have no theory of concepts to guide them.