The mistake made by people who believe omniscience and free will are not compatible is the failure to distinguish between knowledge and agency. When the knowledge follows the agency in time it is obviously a separate thing that most people can understand. If George chops down a cherry tree on Tuesday and Mark learns about the incident on Wednesday it is quite obvious that George is the agent of chopping down the tree, not Mark. Mark simply has knowledge of the agency, he is not the agent. What gives many people difficulty and generates massive traffic on discussion boards is the scanario where the knowledge precedes the agency in time. If Mark had a crystal ball and on Monday saw in it George chop down a cherry tree the following Tuesday, does that not cancel the agency George has in the matter? The correct answer is that knowledge and agency are separate and distinct things regardless at what time they occur. That is to say that George is still the agent of chopping down the tree on Tuesday despite Mark's knowledge the Monday before that he would.
If however you go to the police and inform them on Monday that a building will be blown up on Tuesday, they will assume you have partial agency. This is very sensible of them because humans don't have the ability to read the future often assumed God has. The police will assume you had some association with the perpetrators of the bombing, willingly, wittingly or otherwise, and require you to answer many questions. While it is highly unlikely that humans can predict the future it remains quite true that knowledge and agency can be different things, especially for God.
A person who knows another person by a very long and intimate relationship such as marriage.might be able to predict what free choices that person will make with alarming accuracy, if perhaps a litte short of complete accuracy. It shold not be difficult however to see that even if their knowledge is extended to perfect and accurate knowledge, the agency of the other person remains.
There is something that is cancelled. Time, not knowledge, does cancel the possibility of making any other choice. George cannot decide on Thursday not to chop down the tree the previous Wednesday if he already chopped it down. It is true that on Thursday he no longer has any other choice what to do the day before, but this still does not change the fact that it was his choice on Wednesday, no one else's, to chop down the tree.