I was speaking of the Abrahamic God. Sorry if I forgot to mention.
Presuming that God must know everything that we will do assumes that time is real. Time is not real in the same way that inches and centimeters are not real. They are a human perception that we ascribe to certain distances or collections of actions as we understand them.
God can know everything that's happening on the Earth in a given moment and infer from what we are doing what action it is that we are about to perform with his infinite knowledge of our capabilities. Even the past is only real because of actions. The ocean pushes sand over bones protecting them from deteriorating etc.. etc.. They don't just magically deteriorate over "time", time isn't real. Time is just a convenient way of describing things that have a tendency to happen consistently. This is also true of the sun rotating around the Earth. It doesn't rotate around the Earth exactly 365 times a year, which is why we have leap years.
Likewise, God didn't create time, he created events. He can be aware of all events that have occurred and all events that will occur and be omniscient, without any need to know what will happen in the future. Now, God predestined his desire for what humanity would become in the Bible, but as it can also be seen time and time again, people do not always succeed at achieving his will. Abraham screwed up the sacrifice of the doves, Noah's son screwed up by covering his nakedness, Judas betrayed Christ and Moses struck the rock twice. These are all perfect examples of freewill interfering with God's desires for what will happen. However, it can also be seen through the Bible that God never ceases to find people who he can work through and who have helped to realize God's ideal of creation.
Lucifer is another perfect example of freewill. God surely knew what Lucifer was doing, as he was doing it, but that doesn't mean that he knew that Lucifer would choose to disobey him before that point. It says in the Bible that we were crafted in God's image, to presume that we do not have free will is assume God does not either.