What are the Sunnah prayers before and after the obligatory prayers, and how many Rak'ahs are for تحية المسجد (greeting the mosque) prayer for each (obligatory) prayer?

The Sunnah (supererogatory) prayers, both those performed before and after the obligatory prayers, are prayed before and after them. They are of two types: emphasized (mu’akkadah) and non-emphasized (ghair mu’akkadah). The emphasized ones are twelve rak'ahs: four before Dhuhr, two after it, two after Maghrib, two after Isha, and two before Fajr. The non-emphasized ones are: four before Asr, two before Maghrib, and two before Isha. It has also been reported that there is a Sunnah of four rak'ahs after Dhuhr. The Salatul-Tahiyyatul-Masjid (prayer of greeting the mosque) is a Sunnah that is attained by performing any two rak'ahs before sitting down.

Regarding congregational prayer, many scholars have concluded that it is obligatory upon individuals, and this is the most preponderant opinion.