Gran Turismo 3: A-Spec
Professional mode:
Select arcade mode, then highlight the "Hard" selection on the
difficulty selection screen. Hold L1 + R1 until it changes to
"Professional".
Selecting series awards:
Series awards (i.e., cars) are not purely random. Press X when
a silhouetted car has the large black circle flashing under it
to cause that car to be selected as the award for winning the
series. Timing is crucial, since the large black circle only
appears under a car for less than half a second. If you are too
slow, the next car to get the large black circle will be selected.