What Dan Mellis asks is "If god is omnipresent and eternal, how could it be that there was a time that people didn't subscribe to the god of abraham?" The short answer is that God is discovered, rather than revealed. People might claim to reveal God, but that would be impossible I think, philosophically. Some people may respond strongly and identify when they hear about God, but that is not the same as revealing God to them.So what is God like then?
I say in my post above to Dan Mellis there is the God that people expect and attempt to describe and then the real one. Often you will encounter revealed religions which purport to describe God to you, but this is not how God is discovered by the Jews. Later on two Christian major theological approaches have been developed called the apophatic and the cataphatic. Apophatic is a positive assertion about God, and it should be limited I think to what you believe. "I choose to believe in God" is cataphatic. Someone else might assume something about God that I don't, so they might make more cataphatic statements. Those would include some who say rubbish like "I know that I know that I know X about God." Then there are negative deductions about what God probably is not. These are called apophatic. A common apophatic statement is "Describing God accurately is impossible."
An agnostic makes no cataphatic statements, but they can still make apophatic ones like "If God is real then God cannot be such & such." There is an analogy in diplomacy. If you believe in peace then very often you can more easily say what does not lead to peace than what does.