الجواب وبالله التوفيق

1. There are two types of na-mehram(marriageable kin) i.e. people who are na-mehram and still related to us and people who are na-mehram but not at all related to us. As per the teachings of Islam, there is complete purdah required from both types. If due to extreme need, a woman is bound to come in front of them, then it is permissible to do so while covering the whole body from head to toe with a shawl etc. (including face, wrist and arms etc.).  
2. It is not mandatory to cover one’s head, face and neck in front of the people who fall in the category of mehram(unmarriageable kin). However if there is a fear of one’s honor and dignity from a mehram, then such a mehram becomes part of the commandments for the na-mehram and purdah should be observed with them as such.
3. According to the teachings of the Islamic Shari‘ah, the woman’s voice also is a part of their satr(objects which should be covered). It is impermissible for a woman to speak or for a na-mehram to listen to her voice, unless there is an unavoidable necessity. Even when a woman has to speak to the na-mehram her voicer should not be soft and gentle.

واللہ اعلم  بالصواب