Answered by Shaykh Faraz Rabbani
Recently, I attended a wedding in a hotel. there was a separate hall set up for maghrib prayers. when we entered to pray, my friend performed 2 rakaats tahiyyatal masjid prayer. Is that necessary in a hall which normally isn’t a mosque?

Walaikum assalam wa rahmatullah,
The prayer for greeting the mosque is only for mosques, not for prayer halls or other places where people pray.
However, there is nothing wrong with performing voluntary (nafl) prayers before the obligatory prayer, in general.
See below.
Wassalam,
Faraz Rabbani