To watch, my favorite is piaffe pirouette on a light connection.  It reveals the real balance and degree of collection.  I cannot stand over bended canter pirouettes.

Imho turns on the haunches or pirouettes should be judged on their training value, and their proper creation by the rider. The requirements in the rules are clear, and the scores should be also.  They are my specialty, and if the comments from judges are unclear go to show management or the judge and require more input.

For the OP: how to tell if the halt is square?  A couple of things should be felt.  Is the horse literally up to the hand, not the rider holding the horse low/closed.  IT maintains te connection with the hand.   If so, the forelegs are square and likely the hindlegs are pretty close.  As far as which hindleg is left, does the rider's fanny feel level or is it rather like standing more on one leg with a tilted hip.  Remember square halts are a result of a horse which is ridden correctly as well as a learned behavior.

There is NO full pass in canter (only in walk and even then it is dangerous as to which legs are crossing over).  There is the vaquero skittering sideways with conterbent meant for bull flighting.  A proper half pass (travers on a diagonal) cannot be more angle than the short diagonal of the GP half pass.  Why?  Because the movement MUST be forward and sideways.