After death, if a person gets accepted into the Planet of the Eternals, they will be re-created from their existing cellular data present on the Elohim Computer which would have been taken long before they died on Earth. So their memories & knowledge of accumulated cataloged information & personality trait will only be as was existing on the day his cellular information was collected by the Elohim & not how they developed afterward and all the memories, emotions, and information accumulated thence. So in a sense, they will not be the same as they were on the Earth. They will not even remember their death, and after 750 to 1000 years, they will die and will have to be re-created. So how can we say they will be the same person living eternally?

The Elohim only collects the DNA of the person at the moment of their death. Their memories are always being backed up so there is no loss.

When they are re-created, they will be in a younger body but with all the memories and experiences they had at the moment of their death.