Salam alaikm. I asking about authenticity of these details about day of Ashurah Assalaam alaikum.. the day of Ashura. Our beloved prophet (s.a.w) used to fast on the day before it and also on Ashura itself. The significance of this day runs back to Nabbi Adam. 1-Its the day on which Allah readmitted him to heaven, 2-Allah drowned Pharaoh and saved the isrealites with nabbi Musa 3-Allah saved Nabbi Ibrahim from d fire where he was thrown by Nimrod. 4-Allah saved nabbi Nuh/noah and the pple on his ark frm the floods. 5-Allah healed nabbi Ayub/job from the longtime illness. 6-Allah reunited nabbi Yusuf/Joseph with his father &family. 7-Allah revealed the 10commandments to nabbi Musa 8-Allah also saved nabbi Yunus/Jonah from the belly of the fish. 9- It is also said that Allah raised Nabbi Isa/Jesus to heaven on the same day. May Allah enable us fast and May he take away our suffering.

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His Slave and Messenger.

The Ahaadeeth reported in relation to the reason for venerating the Day of ‘Aashooraa' and why the Prophet, sallallaahu ‘alayhi wa sallam, observed fasting on that day is that it was the day when Allaah, The Exalted, saved Moosa (Moses) and his people from Pharaoh as in the following Hadeeth:

Ibn ‘Abbaas narrated that the Prophet, sallallaahu ‘alayhi wa sallam, came to Madeenah and he found the Jews observing the fast on the Day of ‘Aashooraa'. He asked about it and they said: "It is a blessed day. It is the day on which Allaah saved the Children of Israel from their enemy so Moosa observed fast on it." Upon this, the Messenger of Allaah, sallallaahu ‘alayhi wa sallam, said: "I am closer to Moosa than you," and he fasted on that day and commanded (Muslims) to observe fast on it." [Al-Bukhari and Muslim]

Another narration of the Hadeeth reads: "and it is the day when the ark came to rest on Al-Judi (mountain), so both Nooh (Noah) and Moosa observed fast on that day to show gratitude to Allaah." [Ahmad] Shu‘ayb Al-Arnaa’oot classified it in his revision of the Musnad as weak.

As for the other reasons mentioned in the question for venerating the Day of ‘Aashooraa', we do not know of any valid evidence to support them.