A rocket can function in space using conservation of momentum, is steered by side thrusters and can brake by reversing its engines or using small thrusters.
Yes, a rocket would operate in outer space, where there is no atmosphere, because it relies on the principle of conservation of momentum and not atmospheric pressure. To steer the rocket, small thrusters can be used to change its direction by ejecting gas in the opposite direction of the desired turn. To brake the rocket, the main engine would need to be fired in the direction of travel, or smaller thrusters can be strategically fired to reduce speed.