A lingua franca is a common language that is used for communication between people of different languages and cultures. Lingua Franca is not a country, nor it is it located in any specific countries.
Currently, Europe's lingua franca is English. However, not so long ago, the lingua franca of Eastern Europe was Russian (and sometimes German, depending on the proximity of a country to Germany as opposed to Russia).
A national language is a language intended to bind a country together. It is usually the most widely spoken language in the country, but this is not always the case. A Lingua Franca is any language that is commonly used across borders, for ease of communication. English is the most widely used lingua franca in the world. French is still a lingua franca in many parts of Europe. Sometimes, a national language also functions as a Lingua Franca within a country, if that country has many languages. Filipino is the national language of the Philippines, and it is also considered to be a lingua franca within the Philippines because only a small percentage of the people speak Filipino as their first language.
English is the predominant world lingua franca, as it is widely used in international business, diplomacy, science, and tourism. It is often spoken as a second language by people around the world.
Currently, Europe's lingua franca is English. However, not so long ago, the lingua franca of Eastern Europe was Russian (and sometimes German, depending on the proximity of a country to Germany as opposed to Russia).
The lingua franca of India and Pakistan is Urdu/Hindi.
The first lingua franca was likely Akkadian, an ancient Semitic language used in the Mesopotamian region around 2500 BCE for trade, diplomacy, and communication between different cultures. It later evolved into Aramaic which became a major lingua franca in the Near East.
English serves as the lingua franca in many international business settings.
Mozambique is the country you're looking for.
The current lingua franca is English, but that may be set to change in the next few years.
The lingua franca for India and Pakistan is Hindi/Urdu--which are functionally the same language.
The Lingua Franca status is a descriptive term, and not a fixed status. Lingua Francas cannot be preserved. They change with the times.