Is he who prays two rak'ahs with the intention of the Sunnah of Greetings, the regular Sunnah, and Tarawih equal in reward to him who prays each prayer separately, or is praying each prayer separately better?

The regular Sunnah prayer can substitute for the prayer of saluting the mosque (Tahiyat al-Masjid). It is permissible for the worshiper to combine the two intentions to attain the virtue and reward of both Sunnah prayers, according to the saying of the Prophet, peace be upon him: "Indeed, actions are by intentions, and indeed, every person will have what he intended." So, if one prays two rak'ahs with the intention of both the regular Sunnah and Tahiyat al-Masjid, he will attain the virtue of both. It is recommended to pray Tahiyat al-Masjid first, and then the regular Sunnah, if time permits, as this yields greater reward. However, praying Tarawih with the intention of the regular Sunnah of Isha is not valid, because each of them is legislated for a specific purpose, and they do not merge into a single prayer.