Can you explain Church of Christ doctrine to me?

LOL and they say Catholics tell others theirs is the only way to heaven. do you realize that in the past there was no immersion due to the fact there was not a sanitary way to do it.... did everyone go to hell back then? did everyone from the time prior to Martin Luther & Ellen White die without salvation due to the fact - those religions did not exist?? how on earth did Christianity survive with all the lost people....