My 2d worth from what I learnt at CFS in the early 90s. The definition of a full spin (CFS) is 'when the aerodynamic and inertial forces have reached a state of equilibrium'. I like this, if you sit and think about it, it makes sense. Identification of a spin is (CFS again) 'buffet with un-demanded roll'. But how do you know your incipient spin has progressed to a full spin? with some aircraft, it's obvious. With others, not quite so. About half way through my RAF instructing career, the spinning syllabus changes with recoveries from the incipient stage being practiced before full recoveries. The incipient recovery for most types is centralise the controls, close the throttle, recover from the ensuing unusual attitude. Essentially, the current UPRT recovery. If this doesn't work, you are in a full spin and the correct spin recovery for that aircraft type should be applied.