Immortality is not related to all creatures including all human beings. Only God is immortal and his invisible eternal beings (if they exist) are immortals. Immortality cannot be given by anyone. God can do any miracle but I don't think that God has an idea of granting someone immortality.
We are created beings. (The word 'created' is self-explanatory.) That doesn't comes under natural way of life. We are not natural but unnatural beings. I mean we are just robots made of different materials (flesh, bones, tissues etc.,). There are ever existing eternal beings which knew neither death nor birth and God is the chief of these eternal beings. IN FACT THIS IS THE REAL EVER EXISTING PHENOMENON. Human beings can think only like human beings. Their thoughts and intelligence are limited. To know and discover more they must come out of the usual boundary and think freely and independently.
God cannot watch each and every human being at the same time and cannot live with each and everyone to guide them. That's why He had created different kinds of spirits for various purposes. He had made the spirits to watch, guide and determine the destiny of the human beings from their daily activities, talks and thoughts too. Your past determines your present and your present determines your future. God has given freewill to all creatures including human beings. According to this, all human beings have all right to live a life as they wish. But if it happens to be bad and hurts someone, they have to face the consequences. These consequences are created by spirits. It's a natural system. After death no one lives in any form. Heaven and hell are only for spirits. Spirits are separate elements. A human being is not a single spirit. A human being during his/her life time is living with many spirits which have joined one by one since birth. They are knowledge, skills, feelings, emotions, interests and everything. Even thoughts are not your own. For example, when you want to take a decision on a subject, one after another the spirits think and you just listen, choose or reject the ideas which they transmit to your mind through your brain in the form of thoughts. Brain is just a media to connect the spirits to your mind. A mind is just a computer's mind. After the destruction of a computer completely you will not get it's mind. The same is the case with the human beings. Soul is nothing but an energy needed for the functionality of a body. It is not a spirit or anything else. A human being is just a robot made of flesh and bones and a toy of the spirits for their games.