You are referring to the concept "paramatma" or "atman". Every thing that has a begining has an end. Everything ceases. There is nothing permenent, so there is nothing eternal. Buddhism disagrees on that there is something that goes out after death or comes in on birth. But there is reincarnation, until one attains Nirvana, the ceassion of re-incarnation. Buddhism teaches the way to attain this exactly.
Hinduism is a religion that based on the concept of God. But Buddhism is not based on this concept. According to them, gods are a kind of powerful aliens but not deathless. Buddhism was a philosophy based on the concept of cause and effect. Later, some followers of Buddhism converted it to a religion.
The concept does not apply in Buddhism.
There is no offical god in Buddhism, but actually buddhism does have a dharmic god like equivalent, it is called Nirvania.This is the case because in hinduism and sikhism they both believe that god is a peaceful place, home to the soul(atman/jiva) and free of suffering, and buddhism believes in this but calls it Nirvania.
Baptism is not part of Buddhism. This is a result of Buddhism not having a deity, the concept of anyone or thing being able to "purify" anyone else except that person themselves. Even the concept of "purification" is shakes Buddhism has no concept of sin, original sin, damnation, salvation etc.
Buddhism concept is to tame our wild minds and make free from any suffering.- Yeshi
The Nichiren Shu are considered a part of traditional Buddhism. There is no concept of post-Buddhism religions as there is a concept of post-Islamic religions.
atman
Atman is the Hindu concept of "real self", or the purest essence of an individual. A person's emotions, feelings, and thoughts are not considered atman - those are Maya, or illusions. The ulimate goal of Hinduism is to break free from Maya and the cycle of reincarnation and unite with Brahman, the Absolute Reality, which is identical to atman. Thus, self-actualization through meditation and self-discipline is key in order to be one with Brahman.Clemmons, Nancy. Exploring the Religions of Our World. Notre Dame: Ave Maria, 2008. Print.
Buddhists do not worship any person or deity, including The Buddha. Therefore the concept of a Savior that needs to be an intermediary between a person and god in order to purify or redeem that person is not a concept present in Buddhism. Therefore there is no Savior and none is needed for Buddhism.
No one knows, because you cannot see the Atman. The Atman is the observer which no one can observe. Therefore, it is impossible to answer your question.
Sabri Atman has written: 'Assyrier - syrianer'