R = revised. In 2003, the AAMC revised the subject list on the MCAT and decided to emphasize certain topics more than others. They revised the practice tests appropriately. The details are on the AAMC's website, but it doesn't matter to you anyway. All you need to know is that the tests are available and they reflect the material the AAMC will test you on. (They didn't update tests 1 & 2 so they aren't available.) Tests 7 & 8 were released after 2003 so they didn't need to be revised.
I started studying about 5-6 hours a day 5 weeks before the MCAT. I studied all of the topics thoroughly before I took any practice tests. Then I studied the content again. Thoroughly. Then I took 2 tests a week about a month before the test - starting with 3R and going on from there. I studied all the content between tests, but focused extra attention on those content areas in which I didn't do as well as I wanted. I didn't give myself a "mock exam", I just took all 217 (or however many there were) questions straight, but I don't have any problems with timing. (So, if you have problems with timing, I suggest you do something else.) My score on the tests went progressively up and peaked at 7 & 8. I reviewed all of the tests and the answer keys and the content (again thoroughly) the week before the MCAT. My actual MCAT score was one point below tests 7 & 8 so I'm not going to complain. My only advice, get a good night's rest before the MCAT and be comfortable and confident while you take it. Don't worry about other people in the test center. All you care about is yourself.
Others will invariably have different approaches/advice.
Good luck!