Ahsanallahu ilaykum, In my uni a hall is given to Muslims(we use the side) and another hall is given to Christians, other kinds of events/programmes still take place in these halls if the mgt, wants, can this be called a mosque or a musollah and do we do Tahhiyyatul Masjid?

Ustadh AbdulAziz al-Haqqan

A masjid is a place permanently set aside and endowed for the five prayers, so a hall that the management can take back or use for other programmes is not a masjid. So, the two rakahs are not prescribed on entering it.