question #1 Sahih Muslim 410f, Book 4, Hadith 82 : What is the significance of saying ‘Amin’ in prayer and its impact on forgiveness of sins?

The Messenger of Allah (ﷺ) said: When the reciter (Imam) utters:” Not of those on whom (is Thine) wrath and not the erring ones,” and (the person) behind him utters Amin and his utterance synchronises with that of the dwellers of heavens, all his previous sins would be pardoned.