Difference between Nibbana and saññāvedayitanirodha

I read something on reddit that made me think that the author confuses between Nibbana (extinguishment, liberation) and saññāvedayitanirodha (cessation of perception and feeling), thinking that they refer to the same thing. I quoted some of the suttas below that led them to this view. Questions: 1. What is the difference between the two? 2. Are they the same? If they are the same, then when the Buddha returns to the normal waking and talking state, he would lose his Nibbana wouldn't he? 3. What is the difference between the bliss or pleasure of Nibbana in the waking and talking state, compared to the bliss or pleasure of saññāvedayitanirodha? Are they the same or completely different? 4. Is saññāvedayitanirodha needed for attaining arahantship? Can one attain arahantship without ever reaching it? 5. Is it possible that one could attain saññāvedayitanirodha, without attaining Nibbana? They used these sutta quotes to support their assumption that Nibbana and saññāvedayitanirodha are the same: > They understand: ‘There is this, there is what is worse than this, > there is what is better than this, and there is an escape beyond the > scope of perception.’ > MN 7 > When he said this, Venerable Udāyī said to him, “But Reverend > Sāriputta, what’s blissful about it (Nibbana), > since nothing is felt?” > > “The fact that nothing is felt is precisely > what’s blissful about it. > AN 9.34 > “One perception arose and another perception ceased in me: ‘The > cessation of existence is nibbāna; the cessation of existence is > nibbāna.’ Just as, when a fire of twigs is burning, one flame arises > and another flame ceases, so one perception arose and another > perception ceased in me: ‘The cessation of existence is nibbāna; the > cessation of existence is nibbāna.’ On that occasion, friend, I was > percipient: ‘The cessation of existence is nibbāna.’” > AN 10.7 > There are those who would say that this is the highest pleasure and > happiness that sentient beings experience. But I don’t grant them > that. Why is that? Because there is another pleasure that is finer > than that. And what is that pleasure? It’s when a mendicant, going > totally beyond the dimension of neither perception nor non-perception, > enters and remains in the cessation of perception and feeling. This is > a pleasure that is finer than that. > MN 59