You will have questions on the test that you cannot do, so one of the things you have to study is how to identify questions you can't do in 2 minutes and what to do with them instead to still make a good educated guess (that means finding other ways to eliminate an answer choice or two to better your odds when you guess).

You cannot learn how to do every single problem, simply because the test has more than 10,000 questions in its database and, no matter how well you can do, it will give you things you can't do.

The questions from OG that you simply can't figure out - those are good practice for what I described above.