if it can move forward or backward without pressing fuel pedal,

you are not expecting a car, regardless it's heavy or light, can move fast or climb a mountain without pressing fuel pedal. Otherwise, either the idle is too high, or the engine is too big while the car is too small/light.

now if the car doesn't move at all, that is not your car, it could be an indication of impaired movement, such as brake stuck or transmission failure...