From what I can see it was VH-EBV, the newest A330-200 that was unserviceable on 04-Apr. It operated the following night back to BNE as QF62.
The VH-QPC aircraft that operated the delayed flight actually arrived in to NRT on 05-Apr as QF79.
OQI is out of service. Tomorrow’s schedule looks unaffected at this stage, after QF11 on Tuesday and Friday were cancelled, so OQI must be due back in service tomorrow at this stage.
Probably crew rest requirements rather than aircraft related. Yesterday’s QF1 delay will mean they have they a crew out of position. The crew due to operate tonight’s QF2 were probably the crew who were delayed 24 hours on QF1