What is the wisdom behind having two Adhans for Fajr prayer, and is it permissible to pray after the first Adhan? And is one to stop eating and drinking (for the fast) after the first Adhan or the second? And what is the ruling on performing the Fajr prayer upon hearing the Adhan from any mosque?

There are two adhans for Fajr: 1. The first adhan: This is at night before Fajr, to alert the one who is praying (qiyam al-layl) and awaken the sleeper to prepare for prayer and suhoor. At this adhan, one does not abstain from things that invalidate the fast, nor is the obligatory prayer performed. 2. The second adhan: This is at the entry of the time of Fajr as-Sadiq (the true dawn). At this adhan, the fasting person must abstain from things that invalidate the fast, and the time for Fajr prayer begins.

The prayer time begins with the entry of Fajr, i.e., after the second adhan.