Don't know what to tell you re #2, but just a bit of caution re #1. At least when we did this on SFO-SYD-MEL-SYD-break for 5 days in SYD-SFO a couple of years ago, it was a bit confusing re what to do when deplaning in SYD both times and on the outbound there was a long security line in SYD (though we made it to the MEL connection somewhat comfortably). So you might review other threads about this here in the UA forum and in any event make sure UA ground personnel tell you where to go when deplaning in SYD.

Or perhaps it's a lot clearer now. Or perhaps we're just easily confused.