Is the niqab an obligation or a Sunnah, and what is its evidence? Is the hadith about a woman in ihram removing the niqab and gloves evidence for this? How does a non-niqab-wearing woman enter into ihram? And does a niqab-wearing woman receive a great reward for her patience in intense heat?

Covering the face is obligatory according to the most preponderant opinion among scholars. A woman uncovers her face and palms when entering into ihram (definition) for Hajj or 'Umrah (definition). What is obligatory upon her is not to cover them with gloves and the niqab specifically, but rather to let down something from her head covering over her face without it clinging to it. The reward is commensurate with the hardship.