None of us can really ever know until we die, maybe even if we've had an NDE, it might just be a secret compartment of our brains reserved for death, but if it is experienced as real then what stops it from being real?
What seems contradictory to the teaching of the scriptures though, is that a lot of them, ( and I've seen a lot if them ) claim to have been saved by God and have seen heaven even though they were non believers in life, whereas scriptures tell us this is not possible unless we have given our lives to God whilst we are alive.
Personally I'm keeping an open mind, I think the way we have lived our lives are stored in our brains and in our soul are what we will face when we die.
As for false prophets, I have no reason to believe they are all lying, especially when you see how moved and changed they are by their experiences, could it be they were used by God in the way Jesus used sinners to spread the word of God?
As far as hell is concerned, I also knew about my father's repeated nightmares about where he was going after death in the last years of his life, and I don't think it was any coincidence that he had done some truly wicked things in his life that he refused to even acknowledge let alone apologise for.
It was enough for me to take the health of my soul more seriously as what he told me frightened me, as it was identical to descriptions of NDE's I had heard, and my father had no access to these descriptions so there was no chance of copying.