Good questions and answers!
1.) Correct.
2.) Those quotes were discussed in the post “Ānāpānasati – Overview.”
Anyone should try to practice Ānāpānasati/Satipaṭṭhāna Bhāvanā.
– Of course, one in category (i) would not have any incentive to do.
– Those in category (ii) should do it, and it will help them comprehend 4NT/PS/Tilakkhana and get to the Sotapanna Anugāmi stage.
– Only those in category (iii) (Sotapanna Anugāmi or above) can attain higher magga phala with the practice.
There are two posts (including the one cited above) in the section “Elephant in the Room 3 – Ānāpānasati.” I will write more in the future.
– There are also early posts on Ānāpānasati in “Bhāvanā (Meditation)”
– Posts on Satipaṭṭhāna in “Mahā Satipaṭṭhāna Sutta” section.
P.S. This topic is more suited for the “Meditation Forum.” Please think about the appropriate forum before posting.