Did you really say the only way God can know that something is going to happen only if it happens? Doesn't He know what's giong to happen even if the person doesn't do it? What about Abraham & offering up his son Isaac? [Genesis 22:1-19]
Why did God have Abraham go through with the test of whether he'd sacrifice his son or not since He already knew what he'd do? [Genesis 22:1-19, Genesis 3:8-9, Genesis 4:9, Genesis 18:20-21]