they wouldn't be able to vote in an election because you cant have any criminal records to your name if you want to vote in an election
Japan would have treated Australia no different to the way they did the people of Nanking after China's troops lost.
Absentee
There is no way that could have happened the typical (election) way. If the President suddenly turned black, I am sure most Americans' heads would have exploded.
with a population of 21,374,000 I would venture to guess that there would have been several.
I would call it a direct election.
national
It did happen several times, and what happened was, the office of Vice President remained vacant until the subsequent election. In terms of Presidential succession, the next person in line (Speaker of the What_if_a_vice_president_died_before_the_25th_amendment) would have "moved up" had the President died or resigned, but that never happened.
The president would be the person who came out on top in the election; the person in second place would be vice president.
local
It would depend on local legislation
It is quite possible that the French would have carried through with their claims to Australian territory, and most people would now be speaking French in Australia.
You will turn into stone.