1) If you mean "engineers plate", yes you need that. This is different to an official compliance plate as on the SEVS or older system for cars newer than 15 years. It basically says "this vehicle meets ADR's for 1989"
2) yes, you will need the aussie VIN attached to the firewall, which is at the bottom of your import approval.
3) See point 1).. no.
I registered mine after compliance.. there were a few confusing stories I got, but in the end I spoke to the manager at QLD transport, and what i thought was correct.
You basically just need the above, a valid safety cert, the CTP papers, and your import approval (they check this). That is all you will need. You will have to also pay stamp duty, and a little bit extra for the issue of new plates.