Is The World Eternal. Is The World Not Eternal? Is The Soul the Same As The Body? Is The Soul Different Than The Body?

The Buddha said:

Why have I left that undeclared? Because it is unbeneficial, it does not belong to the fundamentals of the holy life, it does not lead to disenchantment, to dispassion, to cessation, to peace, to direct knowledge, to enlightenment, to Nirvana. That is why I have left it undeclared.

---Culamalunkya Sutra---