No – Google Maps does not show the official trail. Use specialized apps (Buen Camino, Wise Pilgrim) or OpenStreetMap-based tools (Mapy.cz, OsmAnd).
May–June and September–October. July–August can be very hot; winter brings snow to the Puerto del Palo. camino primitivo route map
Yes, especially in small mountain villages (Grandas de Salime, Berducedo, La Mesa). There are fewer albergues than on the Francés. No – Google Maps does not show the official trail