Australia, who is fully in the Eastern Hemisphere, does not border any other continents. Antarctica, who is partially in the Eastern Hemisphere, does not border any other continents as well.
Asia
No. Australia has no land borders with any other continent.
Poland is in Europe and does not border countries from any other continent.
The Southern Ocean surrounds the continent of Antarctica and does not flow around or border any other continent.
Australia is the continent with the shortest land border, as it is completely surrounded by water with no land connections to other continents.
russia
The Urals mark the border of Europe and Asia.
Ibo people in eastern Nigeria
Scotland shares a common border with England but has no border with any other country.
Other than bodies of water, the border of North America is the Panama-Colombia border.
Ibo people in eastern Nigeria