Car will not depress brakes, so the key will not turn to start it.

Hello, There is nothing to prevent the vehicle from the brake pedal being depressed, except a mechanical failure of the master cylinder or brake booster. If you move the brake pedal at all, the brake lights on the rear of the vehicle should illuminate, plus the indicator to press the brakes on the dash should turn off. The more likely issue is that the steering wheel is too difficult to turn, possibly because of the hill, or that the wheels are bumped into a curb. This just means standing on the brake pedal while putting your body weight into turning the steering wheel to unlock the ignition switch. If I do not understand the issue, let me know.