“I read the story of Upatissa and Kolitha (Ven. Sariputta and Moggalana) becoming Arahant in one lifetime (by attaining stages after stages on different occasions), therefore it should be possible to attain Arahanthood in one lifetime (in this case one human jati).”
Yes. One could attain the four stages of magga phala in one lifetime.
– But that person would have practiced Buddha Dhamma in MANY previous lives.
– There has been an infinite number of Buddhas in the past. Even though our planetary system is destroyed periodically (over many billions of years), it reforms too. That process goes on forever. So, we all have learned Buddha Dhamma, even most likely listened to a Buddha, in our LONG past.
– I recommend reading that post I provided in my previous reply AND the references there. This takes some effort to understand. Another specific post to read is, “Infinity – How Big Is It?”
You wrote: “The urgent goal in this lifetime for us REALLY IS attaining Sotapanna stage, because it acts as a “brake” from this Samsaric Circle in which we have suffered for too long. This is in line with your other article (I do not remember which one).”
That is correct.
You wrote: “The Arahants mentioned above must have started on the path long long ago, but for some reason hasn’t yet attained any stages, which results in a really long wait time. Unfortunately there is nobody who can accurately tell us whether we have reached any stages or not, so we should keep striving to stay on the path.”
No one else (unless it is a Buddha) can tell whether someone has attained a magga phala.
– One WILL KNOW when one attains a magga phala (if one has learned Buddha Dhamma).