Imran,
Phase 2 & 3 is almost identical to CTC phase 2 & 3, with some slight difference in the group discussion tasks. If you make the grade for CTC but not Qatar, you'll still be offered a place at CTC.
As far as whether you'll be going to Doha or not, not many of us could give you the answer. I'm not sure about NZ, but round here in the UK, we've been told to wait for Qatar to come over here.
As far as practice aptitude tests go, I can't speak for anyone else, but
this is what I used and it seemed to work for me.
Hope that helps.
Charliegarner- so you've been waiting since September?? QCA - would that be the Qatari equivalent of EASA?