If you are form Australia than no need to passport to travel < a href=http://www.cruiseeasy.com.au/>cruise Australia.
Yes, everyone needs a visa to enter Papua New Guinea beside it's own citizens and permanent citizens.
If you are a US citizen, you will need both a valid US passport and an Australian ETA visa to travel to Australia.
no. Only people get passports.
yes
No, if you buy a house in Australia they will not give you an Australian passport. You need to apply for an Australian passport, and you can only do that by becoming an Australian citizen.
You'll need a US PASSPORT to return to the US.
No, but you do need a valid passport.
Yes, sure !
Yes
Where are you from? What country's passport do you have? If you're an EU or EEA citizen then you don't need a visa for travel within the European Union or the EEA (Norway, Iceland, Liechtenstein). I'm from Guinea and I have Guinea passport. Then you will need a Schengen visa. You need to get it from the Spanish embassy in Guinea. The visa will be valid for all Schengen countries.
If you are not an Australian citizen or permanent resident you need a visa to be in Australia.