(b) That's right. It used to be the case that, in relation to occupiers of land or premises, special rules were applied to decide the extent of the duty of care that was owed to persons who entered property and were injured. The old rules drew a distinction between invitees, licencees and trespassers. But this approach is no longer applied. In 1987, the High Court decided that the ordinary rules should be followed when deciding the extent of the duty of care owed by occupiers of property to persons entering their land or buildings.
In fact the old rules had long been thought unsatisfactory and legislative changes to the law were introduced in some jurisdictions, just before Zaluzna's case was decided, to make the ordinary rules applicable.
In the present case, A cannot rely on the old special rules. Further, it seems at least possible that, applying the ordinary principles to the circumstances, A would owe a duty of care to B as a member of a class of persons who would foreseeably enter the shop through a rear or side entrance and who would not therefore see the warning notice at the front of the shop. Also see Wyong Shire Council v Shirt (1980) 146 CLR 40.