Why did God allow Hitler to kill millions of innocent lifes? Why did God allow war, diseases, and suffering?

Is God selective? Why does He bless some people while others seem to go without?

Why didn’t God reveal Himself clearly to humanity before the time of Christ?

If God is all knowing and know our future and know what will we do, do we have free will?

Why would God create a man (Adam) knowing that he will sin and still go to Hell if God is all knowing?