The mind is not some, albeit complex, machine-like thing. Or some kind of mathematical object. It's not something that, if you know enough of it, you can know it all. It makes no sense to say 'God knows our minds perfectly' as if that meant that God can predict exactly what we will do in any given situation, how we will react to the new recipe your mum is going to make for you next week. Etc. God will know how you react, when you react. So long as he finds it interesting enough to watch you. Because the mind, aka, the human being is a relational thing, a living thing. Being itself day after day, moment after moment. The question is not what can you know about it but how do you relate to it and what is its role in the world?