It's very unlikely to be allowed. But you'll never know unless you call and ask the FF program.

I am with SQ. At one time, I was trying to make a booking SIN-LAX-KOA(Hawaii). It is the only routing possible between the origin and destination. They told me it was backtracking and I needed to make 2 separate bookings.

IMO, backtracking is not so straight forward to define. Because SQ allows award routing like MEL-SIN-DPS. So, although unlikely, ANZ may allow PER-MEL-AKL. No harm calling them and check.