You don't have to be an Australian resident to get an OZ licence, but as soon as you do the licence that you have obtained here, overrides your O/S licence. There is no obligation to surrender an O/S licence once you obtain a licence here, nor is there any Authority that can make you surrender it. you may very well be travelling between two countries and require your O/S licence every once and a while when you travel O/S.
In regards to the first question asked though, you'd be treated as an un-accompanied learner.
I had this exact same thing where I nabbed an Indian guy doing 150 late one night with his wife next to him. Pulled him over and he produced his Indian licence. I went back and did my checks and found that he had a NSW learner's permit. So he had issues with regard to the speed and no 'L' Plates.
I then went back and asked the lady if she had a full Australian Licence and she said 'yes' and could only produce her passport for ID. I go back and do a check and, of course, she also had a NSW L licence.
So she gets one for give false/misleading information to police and he gets another for being a 'learner un-acompanied', well actually she got the ticket and I sent him to court.
Second over 45 offence (mind you with an 80kph speed limit for L plater's he was actually 70k's over) His Honour was a little cranky with him since when I got him he had only had his licence back from suspension for the previous speeding offence for about 10 days. He copped 3 years Disqualification, $2,500 fine for the speed and $900 for unaccompanied, and His Honour let the no L plates slide...
Some people are idiots!!!