Always interesting to see your own city through someone else's lens. Just a few fact checks
Chadstone is not a Westfield, it's owned by a different group (Vicinity). It's the largest by floor area in the country and random useless fact: it's nearer the geographic centre of Melbourne's population than the CBD.
Flinders Street is the main metro trains station (all trains will pass through, most have Flinders St as the origin or destination), Southern Cross is the main regional station & coach terminal (although it has a very high metro patronage as Docklands is on one side and the CBD the other).
The Melbourne Metro tunnel project (SpongeG posted a few pics of the Domain station construction site on St Kilda Road) won't have a stop at South Yarra and it won't go near Prahran.
Melbourne's estimated population just ticked over 5,000,000 in the past few weeks. We always talk about metropolitan populations - local councils are small and really not comparable to North American local government (City of Melbourne, an area of barely 50 square kilometres, has about 135k people). To highlight it, SpongeG took photos in three different 'Cities' (Melbourne, Stonnington and Port Phillip) in the photo set above, and they're all adjacent to one another - Chadstone (in Stonnington) to the CBD (in Melbourne) is 10km, St Kilda (in Port Phillip) is ~2-3km from South Yarra (in Stonnington)).
Melbourne's
CBD is the most densely populated part of Australia, Sydney has many more densely-populated sects than Melbourne does in the top 20.