question #1 Sahih al-Bukhari 556, Book 9, Hadith 33 : What is the significance of completing a prayer if one manages to perform one rak`a before the specified time ends?

Allah’s Messenger (ﷺ) said, “If anyone of you can get one rak`a of the `Asr prayer before sunset, he should
complete his prayer. If any of you can get one rak`a of the Fajr prayer before sunrise, he should
complete his prayer.”