question #1 Sahih al-Bukhari 5261, Book 68, Hadith 11 : What are the conditions under which a woman can remarry her first husband after being divorced thrice?

A man divorced his wife thrice (by expressing his decision to divorce her thrice), then she married
another man who also divorced her. The Prophet (ﷺ) was asked if she could legally marry the first
husband (or not). The Prophet (ﷺ) replied, “No, she cannot marry the first husband unless the second
husband consummates his marriage with her, just as the first husband had done.”