The difference between rupa jhana (corresponding to the mental states of rupa loka Brahmas) and arupa samapatti (corresponding to the mental states of arupa loka Brahmas) is pointed out in #5 of “Samādhi, Jhāna, Magga Phala – Introduction.”
- It must be clear that there is no 9th jhanic/samapatti state per Zapper’s question.
- Once one transcends the fourth arupa samapatti, one attains Arahanthood.
- Ancient anariya yogis (including Uddaka Ramaputta mentioned in the Tipitaka) were able to proceed all the way to the highest arupa sampatti (nevasaññānāsaññāyatana). But they could not transcend that (and to separate from the world, i.e., get to Arahanthood) because all of their samyojana (sansaric bonds) remained intact. To break those ten samyojana one must comprehend the Four Noble Truths/Paticca Samuppada/Tilakkhana. As explained in many posts, it is a stepwise process for a puthujjana (via Sotapanna, Sakadagami, Anagami, Arahant).
- Our Bodhisatta achieved that during the night of his Enlightenment (and became a Buddha).