Start Championship Mode and enter IGN64 as your h3.
All GT2 Circuit Cars
At the Main Menu press Z Right Z Z Z B CDown A Right Start on Controller Two.
All Cars and Tracks
In Championship Mode enter RACES THE BEST as your h3. Then on the next screen that appears press Left Right Right Left Down Up.
All Sydney Tracks
First remove the memory pak. Then start a new championship and enter FROZENSKY as your h3. Accept an offer from one of the two teams and return to the Main Menu. Select a quick race. Choose any of the race modes to access the Sydney tracks. Again return to the Main Menu and insert your memory pak. Save your career so that when the game is reloaded all the Sydney tracks will be available.