What is the ruling on the first Adhan for Fajr prayer and Jumu'ah prayer? And does it carry the same virtue as the original Adhan and responding after the caller?

The first Adhan before Fajr is a Sunnah intended for people to wake up for the night prayer. It does not prohibit food for a fasting person. As for the first Adhan before Jumu'ah, it was initiated by Uthman, may Allah be pleased with him, to inform people of the approaching time for Jumu'ah. The listener's repetition after the Muezzin and supplication at these two Adhans carry the same virtue and reward as the Adhan for the obligatory prayer, due to the generality of the Hadith: "When you hear the Muezzin, say what he says, then invoke blessings upon me..."