John 3:13 (Jesus was the first to Heaven), does not preclude the repeated incarnation of a particular (human) dimension of Christ. It would restrict it to a time after Heaven was opened to all. Recall also that Jesus was speaking of humans of his era. Those angels obtaining Heaven before Jesus existed did so by inclusion into Christ, the Son of God directly. If parallel earthly type worlds exist, they would follow their own time system and would not be subject to the John 3:13 time line of our world.
NDE patients undergoing clinical death always return to life, and NDE visits themselves are neither reincarnation nor the ongoing incarnation of Christ. The earliest known NDE report is written by Plato, in the tenth book of “The Republic”. NDE’s are really visits to the afterlife, or the boundary of Heaven and they are recorded throughout Church history, the apostle Paul made such a visit, (2 Corinthians 12:1-10).