question #1 Sahih al-Bukhari 1228, Book 22, Hadith 5 : What should be done if a mistake is made during the prayer?

Once Allah’s Messenger (ﷺ) offered two rak`at and finished his prayer. So Dhul-Yadain asked him, “Has the
prayer been reduced or have you forgotten?” Allah’s Messenger (ﷺ) said, “Has Dhul-Yadain spoken the
truth?” The people replied in the affirmative. Then Allah’s Messenger (ﷺ) stood up and offered the remaining
two rak`at and performed Taslim, and then said Takbir and performed two prostrations like his usual
prostrations, or a bit longer, and then got up.