RE: 3D Vs 4D
3D aerobatic flight includes flips, rolls, piros, and/or combinations of all three with little or no ground speed. 4D doesn't exist, unless you count flying through wormholes for the entertainment of other galaxies. Some guys who quickly shake the cyclic stick (it averages out) through maneuvers for the resulting blade sound effects seem to think that they're in another dimension but they're really still here on Earth the whole time. It's fun to watch, but hard on blades, bearings and dampeners.