Welcome to Flyertalk. Let's begin by clarifying some of the codes.

VA is the IATA code for Virgin Australia, but I think you mean Virgin Atlantic which is VS ?

SA is the IATA code for South African Airways, but since you want to go to Singapore I image you mean Singapore Airlines which is SQ ?

Using miles or points to upgrade from economy class is tricky because not all airlines permit mileage upgrades from the lowest economy fare classes -or- they require a cash co-payment in addition to the miles -and- often you cannot upgrade using partner miles. Have you researched the upgrade rules of the airline you propose to fly?