There is no country that borders three continents.
Wabash, Ohio and Mississippi respectively
The answer depends on what kind of borders you are asking about. Almost every country has at least three borders if you include such borders as those between governmental divisions such as counties, states, provinces, territories, etc. And there are land borders and water borders.
There is no country that borders all three countries.
Germany borders three other countries in Europe: France, Belgium, and the Netherlands.
I think Bangladesh is surrounded on three sides by water.
Historically it has, but currently it only borders the Black sea.
Canada
Nicaragua is located north of Costa Rica. The country of Panama also borders Costa Rica to the south. All three countries is located in South America.
Germany is a single country, with no other countries within its borders.
Three countries can be said to border Brazil and Argentina, they are Bolivia, Paraguay and Uruguay.
All three of these cities are in SOUTH KOREA. Seoul and Inchon are in the northwestern part of the country, while Busan is in the southeastern corner of the country.