FIRST class Oslo to Sydney 4180€ with Etihad Suite, stopover in Abu Dhabi is for free. You need to route via CDG or LHR, otherwise your flight to Abu Dhabi is only in Business class.
Best availability to fly via LHR is on Fridays, the short flight Oslo to London is not in First class, but that's only a bit more than 2 hours.
PERMITTED 07JAN 19 THROUGH 30JUN 19 OR 11AUG 19 THROUGH 31OCT 19 ON THE FIRST INTERNATIONAL SECTOR.
TICKETS MUST BE ISSUED ON/BEFORE 14APR 19.
TRAVEL FROM TURNAROUND MUST COMMENCE NO EARLIER THAN 3 DAYS AFTER ARRIVAL AT TURNAROUND.
TRAVEL FROM LAST STOPOVER MUST COMMENCE NO LATER THAN 4 MONTHS AFTER DEPARTURE FROM FARE ORIGIN.
2 STOPOVERS PERMITTED ON THE PRICING UNIT - 1 IN EACH DIRECTION LIMITED TO 1 FREE AND 1 AT EUR 50.00.
Here's an example via CDG