Yes, the earlier tests are great for drilling/learning on. This way you will have plenty of tests to take as full-timed PTs when you are ready. Generally people use PTs 1-35 for drilling and then 36-80 for full-timed exams.
Not yet anyway. However, I agree that one should typically use PTs 1-35 to drill games. Then, like @JustDoIt recommends, drilling any games you have trouble with after taking PTs.