Need Gran Turismo 4 help please

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I can't access extreme events or the world championship events on Gran Turismo 4. I have earned all licenses and finished first in all beginner and professional events, and have double checked again and again to make sure I have all gold trophies in the beginner and professional events. Do the beginner and professional events have to be completed in a certain order or something. I have been told at other forums that I have to also win the Championships, not just the individual races, but can't seem to get an answer as to what "championships" they are referring to. The beginner and professional events do not list any "championships", only the names of the events, such as Sunday Cup, Tuning Car Grand Prix, etc., and then the names of the tracks for each event. Somebody please help me and call me stupid if you want.