I have heard that Sayyidina Ali once offered a prayer in a drunken state and made mistakes as a result of which a verse was sent down prohibiting Khamr. Is this authentic history?
This is a false narration fabricated by the enemies of Imam Ali (AS). The narrator is Ataa' ibn al-Saa'ib عطاء بن السائب who is mentioned in main Sunni books of Rijaal as a rejected person. Yahya Ibn Mo'een said about him: His narrations are not valid. Ahmad Ibn Hanbal and al-Dhahabi and Abu Haram and al-Nasaa'ee and ibn'Olayyah and al-Humaidy spoke against him and his narrations.
Wassalam.