What is the correct form of the Tashahhud, and is it necessary to move the index finger, and to what extent is the saying of the Messenger of Allah, peace and blessings be upon him, "Indeed, it is more impactful on Satan than iron," authentic or weak?

Wagging the forefinger during the Tashahhud is recommended by the Malikis. We have previously explained the scholarly differences regarding its movement and placement in previous fatwas. As for the aforementioned hadith from Ibn Umar in Musnad Ahmad, "They are harder on Satan than iron," Al-Arna'ut deemed it weak, while Al-Albani graded its chain of transmission as good.