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For a loosely defined itinerary such as the one described above it is difficult to ascertain whether or not an around the world type ticket is suitable, and if so which one. At least without further information.

For example there are plenty of places in Africa that Oneworld does not serve, and intra-Africa travel on Oneworld is limited to a few places in southern Africa on a British Airways subsidiary and a few places in northern Africa (via European hubs). That doesn't necessarily mean the RTW ticket can't be used to cover the longhaul flights and travel within other regions but may restrict destinations or may mean you need other tickets as well to go to the places you wish to visit.

Papua New Guinea is not accessible on a One World Explorer fare because no oneworld airline flies there (Qantas flights are all codeshares on Air Niugini). However, you can fly to Brisbane or Cairns, from which it is easy to get to Port Moresby (on a separate ticket).