I am not a free speech absolutist, but I don't know that free speech in Australia is lacking very much compared to any other English speaking country, including America: I don't really believe that your constitutional right protects you the way that you might think it does, assuming you're American.

As to the latter point, no, that's incorrect. There were some issues in the past with getting a game approved at a 15+ age rating instead of 18+, but those have gone by the wayside as videogames in general have become more mainstream & accepted.