I see in FAQ that this date is National Day, can any one advise as to what happens on this day.? Are there festas ? Do shops or banks or businesses take a day off ? etc etc.

yes everything is closed, it´s a national holliday. obviously not restaurants, tourist shops or great commercial areas.

usually there´s only a militar parade at lisbon and a few politians speeches.

Thanks for info Lukyluke, much appreciated.