Driving on the sidewalks:
You can drive on the sidewalks regardless of what the manual states. Just drive slowly and do not hit any signs, cars, or other objects.
Begin game play and find a long straightaway. Accelerate until your car is over 100 mph. Release the accelerator (and burn out if in use). Hold the cruise control key to keep speeding up.
"Take A Ride" invincibility:
Play a carnage movie (assuming one was created). After it is completed, play Take A Drive, and you should be invincible (excluding running into buildings).
After completing the game, you can drive any car that you drove in the missions, including the truck with the explosives, the taxi, the police car (honk the horn for sirens), and others. You can also access all of the cheats (including the Newcastle Level), but you can only drive the different cars in Take A Drive mode. Additionally, you can play any level in the game.