Point a. True - all gun owners had to register their guns, or run the risk of having an illegal firearm. So you required both a licence to own a gun, and the gun had to be registered.
Point b. Kinda true. Confiscation is a bit strong. Automatic and semi-automatic rifles and most handguns were unable to be registered and had to be handed in - the owners were paid for them.
Ordinary bolt action rifles and other "non-automatic" rifles were allowed to be kept provided you had the necessary permits, but there are fairly strict rules as to how you can keep them. They have to be locked up in a specified type of case - you can't just have them sitting on the wall. If you didn't want to be bothered doing this, then you could hand them in and you would be paid for them.
Most handguns had to be handed in unless you had a bloody good reason for having one - member of a pistol club, or something like that.
So, yes, there are still people who have guns around Australia, but we don't sell them in K-Mart, or places like that. In fact, there are not too many gun shops around Adelaide - at last count there were about 15, in a city of more than 1 million people. Personally I think that this is a good thing - it makes people come up with far more inventive ways of killing people :) Like vats of acid in disused bank vaults and things like that. (Trust me - that happened).
Point c. Probably true. The Kangaroo is not an endangered species in Australia, and it is highly probable that our trade people are out there looking for markets for roo meat. Given that we are now a significant primary producer of grain, beef and lamb, too many kangaroos can really spoil your day, (pity they were here first) and also given that they have indeed been here far longer than white fellas, sheep or cows, they are damnably well adapted, and breed very successfully.
If we feel we need to shoot them, and indeed there are a powerful lot of them, it is better to use the meat rather than pile them up and burn them. The meat, by the way, is very low in fat and cholesterol, and quite good eating, if you like strongly flavoured red meat dishes.
And last but not least, please save me from the comments about eating our national emblem on our coat of arms. That is an accident of history.
Maybe we should do what England did and choose animals like the Lion and the Griffon. You don't see many Lions in England these days, (did you ever?) so they are safe from having to kill and eat one of them, and I haven't noticed any Griffons about lately either. That was smart. Us silly buggers picked two real live animals, so that when we shoot them and eat them, the whole world is up in arms.
The explosion in Kangaroo numbers is not really as a result of the gun regulations, though. It would have happened anyway. More, it is caused by us growing lots of good food and storing lots of water for them to drink, hence they breed up.
This post got a bit rambly & out of hand. Hope you don't mind!