if God can ever know (if He so chooses - very conveniently!)...

if God can ever know (if He so chooses - very conveniently!) what I will do in the future, that means what I will do in the future is already predestined, and not based on free will at all.
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True, God can foresee certain events, but in many cases, he has chosen not to use his foreknowledge. Because God is almighty, he is free to exercise his abilities as he wishes, not according to the wishes of imperfect humans.
The Bible teaches that God is selective when it comes to foreordaining the future. For example, God foretold that “a great crowd” of righteous humans would survive the destruction of the wicked at the end of the present system of things. (Revelation 7:9, 14) Note, though, that God did not give a specific number for that great crowd. The reason? He does not predestinate individuals. God is like the loving father of a large family. He knows that at least some of His children will reciprocate His love, but He does not predetermine the number.

By means of his servant Moses, God said to the nation of Israel: “I have put life and death before you, . . . and you must choose life . . . by loving Jehovah your God, by listening to his voice and by sticking to him; for he is your life and the length of your days.” (Deuteronomy 30:19, 20) Had God predestinated each Israelite either to love him and gain life or to disregard him and merit death, His words would have been both meaningless and insincere. Do you believe that God, “a lover of justice” and the very personification of love, would act in such an arbitrary way?—Psalm 37:28; 1 John 4:8.
God’s appeal to his servants to choose life applies even more so to us today, for the fulfillment of Bible prophecy indicates that we are rapidly approaching the end of the present system of things. (Matthew 24:3-9; 2 Timothy 3:1-5) How do we choose life? We do so in essentially the same way as the ancient Israelites did.