If you look at life like a comic strip, or any book for that matter, it may help. You can read the book in any order, flip to the end, do as you wish, but it will have no bearing on the actual story. Being able to see the future doesn't mean you have the power to change it. G-d may very well have that power, but we are told he doesn't exercise it, as we have free will.
It’s much more complex than that. As the Rambam says, and the Tanya and others discuss הוא המדע והוא היודע והוא הידוע
Hashem’s knowledge is itself the existence of all of creation; it is not separated in any way from Him. For anything to have an existence it must be his ידיעה that gives it its existence. He “knows” everything in existence simply by knowing Himself. He, and therefore his ידיעה transcend time. He created time but is not bound by time, therefore his ידיעה (“right now” from a human perspective) encompasses all points in time from the beginning of time until it’s very end, giving everything across all time it’s existence. To say that he doesn’t know at one point in time what is transpiring in another point in time is to to not understand His relationship to time. Since He necessarily “knows” what is taking place across all time, since that is what gives existence to all of creation across all time, that knowledge creates the reality, seemingly leaving no room for any other possibilities. That is the problem.