Yes, God is omniscient. God-Consciousness is in everything and is everywhere, as I have already covered in previous blogs. If God-Consciousness is the very substance of every aspect of our universe, and of all other possible universes, as well as of Himself, He is by definition omniscient. He knows everything that is, because He is everything that is. There is nothing else that exists.
He does not know what cannot be known at this time. For instance, 100 years ago, God did not know what a DVD player was. This is because even the greatest minds in the world had not conceived of a DVD player or anything remotely resembling that creation. Due to free will, we are free to create our own futures. We are God-Consciousness in essence, and in order to enable free will to operate, God-Consciousness has chosen not to view the future within our universe.
God adds to His knowledge as each of us adds to our knowledge. I, in myself, do not know everything, but what I know is adding to the totality of all knowledge that is known. God-Consciousness is that totality, and can be said to know it all – to be omniscient. This continual addition to knowledge is within time.
From a perspective outside time, God-Consciousness knows all there is to know, past, present and future, but within time, He experiences things as they happen in general terms. The ability of clairvoyants and fortune tellers to see the future does not contradict this statement, allowing of course that the seeing of the future is genuine and is not either trickery or the intuitive assessment of potentials, and that God-Consciousness is prepared in that instance to allow that future to be glimpsed. It is like God peaking beneath the blindfold of time if He has reason or purpose to do so.
However you put it, because God is everything, He must know everything, and is therefore omniscient. That is the bottom line.
(Parts of this blog are quoted from The God Franchise)