1. Is it recommended (mustahab) to wear niqab ?
2. Are there any narrations about hijab of Bibi Zahra (s.a) and Bibi Zainab (s.a), what type of hijab they did??
3. Can a women wear t-shirts, pants at home or outside?

1) Niqab is Mustahab.
2) Their hijab consisted of a long Jilbab, flowing, and not transparent.
3) You can wear t shirt and pants at home but not outside unless she wear something on top to cover her arms and her hip and thighs below the knees