First Person View :
Hold Triangle + Square + START. Release all buttons, then press Start again.

Hidden Parts :
On the mission where you protect Balena's "black tail" transport train, wait for it to arrive, then destroy all EXCEPT for the nose of the train. there you will find a quick-reverse booster extension.

Fixed camera view :
While playing a game, hold Circle + Cross + START. The game will pause. Press START to resume the game with the camera fixed at the pre-location.

Return to default view :
To return to the default view, pause the game, then press START to resume the game.

Hint: Using the map helps!
If you press the start button it will show you the map and it will show you your self on the map it will help you a lot.