How long before landing is downtown Sydney seen from the plane?

Isn't it seen after Opera Sydney House?

How long before landing is downtown Sydney seen from the plane?concert venue

See my answer to your opera house question. You can see the city, the bridge and the opera house from the left-hand side of the plane two or three minutes before touchdown if you are landing from the north.

How long before landing is downtown Sydney seen from the plane?events opera theater

depends on your flight path

downtown sydney is right next to the opera house and bridge

you are flying right in from over the ocean and sydney is right on the coast you wont see too much land before landing
if the flight path is right and weather good you will see the whole lot.