“Before the mentioning of “junior mendicants realized a higher distinction than they had before. Did these “junior mendicants” also include non-ariya’s ?”
All the bhikkhus there were at or above the Sotapanna stage.
– I have revised your link to show “tabs” or “markers” and the sutta opens at your first verse.
– At marker 8.1 the Buddha specifically states that the assembly of bhikkhus are all Ariyas. (Translated there as “it’s free of nonsense.”)
– Starting at marker 9.1, the Buddha states that even more specifically. Some are Arahants (at 9.1); some are Anagamis (at 10.1) and so on.
I think that answers your second question as well.
Ānāpānasati can lead to Arahanthood (Nibbana) only if the practitioner has understood that remaining in the rebirth process is dangerous. Then one must CULTIVATE the Nobel Path that one has “SEEN” to get to Arahanthood.
– One SEES the Path with Lokuttara Samma Ditthi at the Sotapanna stage. Then one can follow that path by the practice of Ānāpānasati.
– P.P.S. At the marker 28.1, the Buddha stated that fulfilling Ānāpānasati will fulfil the four stages of Satipaṭṭhāna: “Ānāpānassati Sutta”
However, non-Ariya can do the “mundane version” of Ānāpānasati, and complete the mundane path so that they can comprehend the Noble Truths/PS/Tilakkhana.
P.S. The “mundane version” of Ānāpānasati includes, of course, the following: Taking in good morals and cultivating “good gati“, discarding bad gati, learning (taking in) correct teachings of the Buddha, discarding wrong views by contemplating those teachings and related material (like rebirth accounts, Out-Of-Body experiences, Near- Death Experiences), etc.