Its depends on that person's religion. If they are Christian then you call them Christians, if they are Mormon then you call them Mormon's. Whatever their religion is that is was you call them. Hope this helps you.
People who spread religious ideas are called missionaries.
People who are not sincere are called dishonest and untrustworthy. People insincere in religious beliefs are called hypocrites.
missionaries
they are called dissenters
They could be called Preachers.
the sign of the cross
Those are known as "martyrs".
Well the people were called Celts and their religious group were the Druids.
Religious oppression is one term.
these people were called the Puritans.
Jewish; or religious Jews.
Religious settlements established to convert people to a certain faith are called missions or missionary settlements. These are typically founded by religious organizations in order to spread their beliefs and teachings to new areas and populations.