1. Yes, of course. Down to higher youth level... so Euro u21/u19 championship, SAM u20 etc. All WCQ's, international qualification tournaments etc.
2. Every nationality has a national team, but only the ones with enough players in the database are playable. The Australian team should be playable in even the most minimal databases (though I've never checked).
If you're asking about the A-League then yes, it is playable. However they're still not quite perfect on the rules and technicalities of it. But it's getting better and it's as good as you'll find in a videogame. State Leagues are also in the game, though not yet playable and sometimes not all that well scouted (if you're a state league buff, particularly in the smaller states, and would like to help scout it for the game PM me and I can get you in contact with the Australian researchers), as are the various state institutes (NSWIS, VIS, AIS etc) - though they are yet to be properly integrated into the game.
3. Australia are in Asia and compete in the ACL, Asian Cup etc.