Considering past records and team strengths i guess it's fair to say the mcg test was a must win for us if we wanted to actually win the series.
This test certainly seems like india's must win, even a draw at the scg would feel like a loss to india.
Yep. Actually there's a common misconception that India has always been suited to the scg conditions (ie conducive to spin). Yes they've made some monster scores there and their batsmen have flourished, but India haven't actually won there in a long time. They've won recently in Perth and Adelaide, but drew at Sydney in 1992 and 2004, and lost 2000 and 2008.
2004 in particular they monstered us there, we only took 9 wickets as they declared twice on 700+ and 190 odd. But it was still a draw. This time around however their bowling attack looks really good and capable of consistently taking 20 wickets, a missing ingredient in their previous tours. So if the batsmen fire (which we all know they're capable of) then they could hit back hard here