Son of Buddha, according to your understanding of things, please tell me:
1. Do the various Buddhas who are mentioned in the sutras all have the same "self" or do they have different selves?
Same Self (Enlightenment is of one taste)
2. Does this "self" include everything in the universe,
or is anything excluded from it,
or which does not arise as part of it?
In other words, is there the "true self" and then there's everything else,
or is there just the "true self" and then nothing beyond that?
There is, bhikkhus, a not-born, a not-brought-to-being, a not made, a not-conditioned. If, bhikkhus, there were no not-bor not-brought-to-being, not-made, not-conditioned, no escape would be discerned from what is
born, brought-to-being, made, conditioned. But since there is a not-born, a not-brought-to-being, a not-made, a not-conditioned, therefore a escape is discerned from what is
born, brought-to-being, made, conditioned.
That which is born, that which has become into being, that which is conditioned, that which is dependent, that which is co-arisen, that which is created, that which is unstable, unsafe & prone to decay, that which is the bridge between birth and death, this seat of disease, with nutriment & birth as its cause, will all perish...!
It is not worth clinging to or rejoice in... The escape from this, is
calm, beyond the sphere of logic, being that which is safe and stable, that which is unborn, that
which is not dependent, but sorrow-free, and stainless, this realm is the final ceasing of all states involving any pain, this stilling of all construction, is absolute Bliss, and ultimate