Sir Spiplane
It is confusing for you because you have failed to put in much effort and research. Your questions indicate this and are therefore somewhat difficult to answer.
I am feeling charitable however so I will give you some guidance within the boundaries of my limited knowledge!
1) There are different base areas for First officers and also freighter and passenger fleets, all of these are therefore different and in different currencies. SO = $386,556 HKD Aust based pax FO $110,892 (Freighter earns about 85% of pax approx)
2) Yes there is a duty allowance it is variable also but say about 5% (SO $20 per hour up to 84 hours per month and FO $8 AUD) Once again it depends on base area so take that as a guide.
3) Use the figures above and work it out! Tax is not deducted (yet!)
4) S&T's is not a term I am familiar with
5) See 1 above
6) Tax base? Do you mean tax rate in Hong Kong? See link below but I would say no.
http://www.ird.gov.hk/eng/welcome.htm
7) Starts at about $24000 HKD pcm for SO, nothing for Freighter FO's. IS now up to about $53 000 HKG pcm but depends on renting buying etc. Others may be able to help with this as I am on a base and ineligible.
8) Again not my area, no children!
9) You will be interviewed for a particular position depending on your experience. There may be scope to change if you meet the criteria for the other position.
10) See above.
11) When eligible and seniority allows. In this case I expect you are referring to a SO start with an FO transfer. About 3 years at present.
12) Australia has Airbus pax fleet and 744 freighter fleet (from late July). This could change but you are able to change fleets once per career to get yourself onto a base.
There is a lot of information here on pprune or ppjn and in the interview books.
Good luck, you will need to prepare and research a little better if you stand a chance of success at interview.