What novel by victor hugo became the best-selling book on amazon france following the fire at the cathedral named in question 3?

Notre-Dame de Paris (The Hunchback of Notre-Dame in English)

Explanation:

We don't know what was question 3, but due to recent history and the Victor Hugo connection, let's assume that answer is "Notre-Dame" cathedral of Paris.

Victor Hugo's novel, called Notre-Dame de Paris, was published in 1831.  There were many movies, musicals and other adaptations of that famous novel.   After the fire that destroyed part of the majestic cathedral, Amazon France did record plenty of sales for the book.

In English, the title is The Hunchback of Notre-Dame, in reference to one of the characters of the novel.