Saw a post on one of the forum regarding domain extension .br.com, however to the best of my knowledge official domains are .com.br just like for Australia .com.au? Do you know which one is the correct code than?
What makes you think there can be only one official domain extension for a country? By the way, there is a .au.com as well.
The fact that it's true (with a few historical exceptions like gb/uk, su/ru, cs/yu, etc.) au.com is owned by a private company that sells subdomains to suckers. It is in no way "official".