Just a very minor nitpick: Australia was never a penal colony, simply because the nation didn’t exist at the time of convict transportation. Australia came into being with federation on 1st January, 1901. In the 19th Century, British convicts would have talked about going to “New South Wales” or “Botany Bay”, rather than “Australia”, although the term was soon adopted (which is why I say this is a minor nitpick, because most of us freely talk about “Australia” in a 19th Century context).
So prior to 1901, the Australian continent was divided into several British colonies. These were independent of one another, and there were even customs and excise border posts in some areas (eg. between New South Wales and Victoria). With federation, the colonies became the states.
New Zealand is older than Australia as a political entity.
In general, yes. However there are significant exceptions to this, IMHO. The existence of regional accents in Australia (and probably NZ too) often tends to cause rigorous debate, but I am in the camp that believes the canard that “Australia just doesn’t do regional accents” is false. Sure they might not be as pronounced as in the UK or even American experience, but they’re there. As per my earlier post about Sydney, the vowels here are frequently clipped or swallowed NZ-style, and there are also Kiwis who have a harsh-edged accent which sounds a lot like the traditional Australian one that Steve Irwin used.
South Australia is another place which doesn’t really fit the stereotyped Aussie accent, though they swallow some of their consonants, but they frequently have a slight British edge (to me anyway), and are often incapable of pronouncing ‘L’: “I went to the Adelaide Hiws with My brother Biw in his new set of wheews.”
I briefly met a Kiwi astrophysicist in Gainesville, Florida. He told me that you can take a working-class Brit and tell him to talk with his teeth clenched to keep the blackflies out, and he’ll sound just like a Kiwi.
That might sorta work with a Brit from the south east of England. Antipodean accents are faintly reminiscent of the working class London accent, to British ears. But don’t try the teeth-clenching thing with anybody from Birmingham, Bristol, Manchester, Liverpool, Newcastle… indeed anywhere further north or west than approximately Coventry. Those accents are totally different.