I'm not missing anything.
You are putting the cart before the horse.
You are suggesting that God knows you will choose the red shirt,
for instance .. it could just as easily be the blue shirt.
It is not how you are claiming.
A better way to put it, is that if God knows 100% that you will choose the red shirt, it is because you will "FREELY CHOOSE" the red shirt.
It is not that you CAN'T choose the blue shirt. It is that you don't WANT to choose the blue shirt.
If you HAD wanted to choose the blue shirt, then God would have known that.
It is not that you can't alter it. Whatever you WANT to choose, that's what God knows.
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I've explained all this already to
@Sheldon and
@KWED
The future is fixed, as you say, with what God knows.
It's not that God fixes it. WE fix it by our choice.
..just as the past is fixed by our choice.