parts of countries surrounded by foreign territory is enclave or enclaves.
oklahoma
The Scandinavian countries (Norway, Sweden and Finland) are each called The Land of the Midnight Sun. Technically the territory above the Arctic Circle and below the Antarctic Circle are the lands of the midnight sun but they aren't countries.
Valley
If it is a country surrounded by land and so having no coast, it is said to be landlocked. An open of land area surrounded by a forest is called a glade or meadow. You can have valleys and basins in terms of geographical forms of land surrounded by other kinds of land.
Steppes .
The rules made for making relations with foreign countries is called foreign policy
They are called 'International Borders'
oklahoma
In general terms a professional who does this is called a "diplomat".
Countries do not have affairs in the way you imply in your question. Countries have foreign relations with other countries and the department that deals with these relationships is called the foreign affairs department.A foreign affairs department will have relations with all countries. some of which will be ambassadorial relationships.
Because its located in the middle of South America and thus surrounded by many of the countries of S. America
They are called Embassies or an Embassy:)
foreign interference
Oklahoma
US cellphones will get signals in foreign countries if and only if your provider has collaboration with any provider in that company in that foreign country.This is called "International Roaming".
It is called imperialism
outsourcing