is making a quadcopter hover forwards or backwards possible ? The only two ways I can think of making this happen is by using motors to move the rotors in such a way that they are always vertical and adjusting the thrust accordingly , The second one is using nozzles to direct the flow of air such that it's always downwards , Can any of these methods work and what can be the problems with them ?
A quadcopter tilts in order to point its thrust vector in a direction that is not straight up. This creates a horizontal component to the thrust vector that allows the quadcopter to move along a horizontal plane.
If the motors are typical, i.e. rigidly mounted to the frame, and the rotors are typical, i.e. rigidly mounted to the motor, then tilting the quadcopter frame necessarily creates a horizontal thrust component.
The only way to tilt the frame of the quadcopter and have it hover is to re-point the thrust vector to vertical or to counteract the horizontal component of force. You could do this any number of ways, including gimbals on the motors, swashplates on the rotors (like the main rotor of a helicopter), or with a horizontal fan of some kind that would blow contrary to the horizontal thrust generated by the body rotation.
Of course, the easiest and least expensive way to handle this would be to have a payload or subframe with a gimbal and move your payload. Leave the base quadcopter alone and move just whatever you're trying to move.