Yes, Swahili is used as a lingua franca in much of Eastern Africa and is an official language of 5 countries.
The British Empire was the largest Empire the world has ever known. What they did was snap-up all the undeveloped places and impose their culture on it. This included the English language.
Yes, for many parts of the world it is.
The Swahili language was developed in 1728 as a lingua franca between Arabs and African traders.
Yes, some of the Bantu languages--particularly Swahili--function as lingua francas in central, eastern, and southern Africa.
Swahili and English
The predominant world lingua franca is English.
The lingua franca of India and Pakistan is Urdu/Hindi.
The first lingua franca--seen from a European perspective--was Latin.
The lingua franca in South America is currently Spanish.
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.
Swahili is a Bantu language mixed with Arabic, Persian, German, English, French, and Portuguese.
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.