The one sin Allah not forgive is worship others (Satan, other Gods and partnering God with messengers - ie Jesus) Shirk we call it. 3 types of Christian in the Qur'an, 2 types may go to heaven.
That's about all one needs to know about your religion. The sort of statement made here is a sure sign of a fake religion.
A true religion would be humble enough to accept there is more than one way to know God.
