Well every type of flying would technically be considered 3D flying since we are flying in 3 dimensions. But the current use of the terms refers to the style of flying.

You have regular aerobatics, which involve forward flight type aerobatics like loops, rolls, cuban 8's etc.

Then there are 3D aerobatics. This includes maneuvers such as hovering, blenders, waterfalls, walls, etc.

The 4D thing hasnt really been defined yet. E-flite released a plane called the Tensor4D. This biplane had some strange flight charectoristics that allowed it to perform knife-edge and rolls without elevator or rudder input and other odd maneuvers. But recently 4D has been applied to planes with variable pitch propellors that allow the planes to do reverse maneuvers such as nose down hovering torque rolls, and even flying backwards.