Thinking of what God cannot do is impossible, since god cannot be compared to humanity. God knows about the smallest things you can ever think or have never thought of. His majesty even knows where a leaf is going to fall and when .
God is ultimate. God created us and knows infinitely more than what we know. We prove our theories by what we see everyday, or by evidence. right? God doesn't need any of these stuff since he's the creator of everything including mankind, and therefore his mighty knows about everything.
What we know, say, think, or do, does not affect god by anything. We "humans" are nothing compared to his mighty. We need him, but he does not. He is so merciful for keeping us alive after the sins we commit everyday.
