score:4
The Virgin Australia Earn Airpoints Table is linked from ANZ's Earning Airports page.
Since MEL-ADL is 399 miles (~642km), you would earn 20 Airpoints in business class one-way or 40 round trip.
On trans-Tasman flights if you book an Air New Zealand flight, with an NZ flight number (eg NZ101 or NZ7000), even if it is operated by Virgin Australia you will earn Airpoints Dollars based on the Airpoints Dollars Earned on Air New Zealand Flights table.
If you travel on Virgin Australia flight numbers (eg DJ101 or DJ8000) across the Tasman or on a flight operated by Virgin Australia domestically within Australia you will earn Airpoints Dollars based on the Airpoints Dollars Earned on Virgin Australia Flights table.
If you travel on any other Virgin Australia flight, excluding flights to or from the Pacific Islands, you will earn based on the Airpoints Dollars Earned on Partner Flights table.