No, Antarctica is a continent governed by the Antarctic Treaty.
Antarctica
The largest "county" in Antarctica is Alexander Island, which is an ice-covered landmass located near the western coast of the continent. However, it's important to note that Antarctica is not divided into traditional counties like in other regions, as it is governed by the Antarctic Treaty System.
I don't know about Australia, but Antarctica cannot participate because it has no real residents. The only people that live there are only living there temporarily and only to do scientific research. To participate in the olympics, a county must have some permanent residents to participate in all the events.
There are no countries in Antarctica.
Only one: Antarctica.
There are no cities in Antarctica.
There are no countries on the Antarctic continent, so there are no county definitions either.
Antarctica is the only continent that the Antarctic Circle passes through.
Antarctica only lies in the Southern Hemisphere.
There are no settlements in Antarctica, only research stations.
That would be Antarctica.