The best resource is the book Gnostic Anthropology
by Samael Aun Weor: Read Book Here
I have linked some other articles below:
If I remember right, elemental Buddha's who begin a new cycle of evolution starting again from the mineral kingdom maintain their spiritual progress i.e. the consciousness doesn't forget it's comprehensions
On the other hand, it's to my knowledge that those who progress somewhat but fail to reach Buddhahood devolve and once purified, are able to restart their evolution but, having gained nothing from past experience? Or, does the soul accumulate some progress with every evolution/involution cycle out of the 3000 provided?
It's also curious to me how vastly different a new era would appear to someone after having spent millions of years in devolving and re-evolving animal existences... And considering the approaching apocalypse, what creatures would be available to us on earth once we're able to evolve again?