The former nation of eastern Europe was Czechoslovakia.(now Slovakia and the Czech Republic)
The proper noun (a former nation in Europe) was spelled Czechoslovakia.The country was split into Slovakia and the Czech Republic in 1993.
The Republic of Armenia is a nation and a former Soviet Republic
russia
Brazil
Russia is the largest nation in the world. It is in northern Europe and Asia
Russia.
Spain
The answer is Serbia.
The next largest country in your list would be France, who is indeed the leading agricultural nation in Europe.
Russia has the largest army in Europe and the world (including active or inactive personnel).
democratic republic of Congo