if you were sitting in the quadhellicopter for example engine one would be on the left side. engine two would be infront. engine three would be on your right side. engine four would be in back. engine one rotates clockwise while engine three rotates counterclockwise. if you increase the rpms in engine one you get more torque therefore you get yaw. if you increase the rpms in engine one you get more thrust therefore you get more lift therefore you get roll. by increasing the rpms in engine one you get both torque and thrust therefore you get both yaw and roll. independent control may mean you get only one axis but i do not see it happening here meow as explained above. if engine three decreases in rpms the offset only becomes more sensitive and happens faster.
Nope. INDEPENDENT control means you can change any one without affecting others.
get it flying yet ?