Depending on where the yellow line is painted, 0 degrees Latitude and 0 degrees Longitude is either in the Gulf of Guinea or the Atlantic Ocean. The closest country would be Ghana, closely followed by Togo, Benin and the island nation of Sao Tome.
Australia is closest to there.
The USA, is the country at 40 degrees North latitude, and 100 degrees West longitude. The state of Nebraska contains precise location.
Germany has the latitude of 50N and the longitude of 10E.
The description of "opposite" is somewhat ambiguous. The nearest foreign territory to Puerto Rico is Charlotte Amalie, US Virgin Islands, about 47 miles due east of PR's largest island. Due west about 75 miles lies the eastern tip of Cuba.
Since you did not specify the direction of longitude, the country located at 20 degrees south latitude and 140 degrees east longitude is Australia, while the country located at 20 degrees south latitude and 140 degrees west longitude is France. The location is French Polynesia, which is a French territory.
There's no country, no city, and no permanent residents there."Latitude 90N" is the definition of the north pole. The longitude doesn't matterand makes no difference, since all longitudes converge at the poles.
This point is in Germany. It is surrounded by a few towns such as Werneck and Arnstein. The closest major city to this point if Frankfurt to the west.
The country located at latitude 20°N and longitude 80°E is India.
Mexico City is around 20 N latitude 100 W longitude
The location at 55°N latitude and 40°E longitude is in Russia. Specifically, it is in the western part of the country, near the border with Finland and the White Sea.
The location with 30° S latitude and 60° W longitude is in Argentina. It falls near the city of Córdoba, which is known for its historical architecture and cultural heritage.
The coordinates 25 degrees north latitude and 51 degrees east longitude point to the country of Iran.