How many Rak'ahs are there in Salat al-Raghibah (before Fajr prayer) and how is it performed? And does Tahiyat al-Masjid suffice for it?

The two rak'ahs of Fajr are among the emphasized voluntary prayers (Nawafil) and are called "al-Raghibah" (the desired/meritorious). Their time is before the Fajr prayer and after the dawn breaks. Several hadiths indicate their فضيلة (excellence) and the Prophet's (peace be upon him) eagerness to perform them, among them: "The two rak'ahs of Fajr are better than the world and everything in it."

The two rak'ahs of Fajr are valid as a substitute for Tahiyyat al-Masjid (the prayer for greeting the mosque), but Tahiyyat al-Masjid does not substitute for the two rak'ahs of Fajr, because the latter requires a specific intention.