Hijaab & Purdah

Q: To what extent should  women use their hijab when their husband or others are performing an act of worship in their rooms ?In other words how much of her body should be covered?

Q: Is it permissible for male and female cousins to hug each other and be casual with each other? In many families, I notice male and female cousins hugging and speaking casually. In certain families, I also see brothers-in-law and sisters-in-law interacting casually. Could you give some advice on this issue and inform us of what appears in the Qur'aan and Ahaadith in this regard?

Q: Can a muslim sister at the age of 45 suddenly decide she wants to wear niqab for her remaining years? During all her past years, she wore hijab exposing her face and wrists. What are the prerequisites and stipulations to be adhered to when in purdah? She comes from a very humble home with no car, hence she uses public transport. She has no other option but to do errands like shopping for food by herself. Is that permissible? She is a devout muslim but postponed purdah because of these reasons where she must walk on public roads to take and fetch her child from school. Whenever in public, she feels very vulnerable and guilty. She always considered wearing the purdah but was influenced not to.

Q: Is the wearing of niqaab fardh?