Religion is usually spread by one person impressing another person with their good character, kind heart, and inner glow.
Missionaries are the people who help spread a religion.
Islam spread from Arabia.
If we take time as a measure of the spread of religion,then since its establishment ,Islam is the religion which spread or still spreading rapidly in Asia followed by Christianity.
It spread by Christian missionaries looking for a new place to spread their religion
Islam was the religion that spread from the Arabian Peninsula to Africa.
Migration is cause of spread of religion. As people travel they bring along their religion, and the constitution does not prevent them.
I believe everyone thinks their ewligion is the best religion. If crusoe did not believe his religion was the best, he wouldnot have worked to spread it.
Islam is a religion. Your question is incoherent.
Christianity
Yes.
buddhism
Yes