Is it permissible for a person to sever ties with his sister because her husband had quit prayer and done him harm?
A sister is a blood-relative and maintaining blood-relations is obligatory in Islam. As regards her husband, he should be invited to the way of Allah with wisdom and beautiful preaching.
What is the ruling on not fulfilling a vow?
A vow is a commitment towards Allah, The Almighty, and so, it should be observed as much as possible, and it is impermissible to take it lightly. Allah, The Exalted, Says –in commending the believers (What means): "(Because) they perform the vow and fear a day whereof the evil is wide-spreading." [Al-Insan/7].
A woman has asked her husband for Khulu`, her gold, deferred portion of the dowry and furniture. Is she entitled to that, knowing that her husband doesn`t want to divorce her?
All perfect praise be to Allah the Lord of the Worlds. May His peace and blessings be upon Prophet Mohammad and upon all his family and companions.
Khulu`* can`t takes place save before a judge of Sharia and he has the authority to make the suitable decision in this matter. And Allah The Almighty Knows Best.
* Khulu' is when parties agree to separate by way of consent, usually upon terms such as the wife agreeing to repay her Mahr (dowry) to the husband upon him agreeing to grant Talaq. The iddah period (waiting time after a divorce) of a woman who seeks a khula, is one menstrual cycle or one month if she is post-menopause i.e. ceased menstruating. This is to ensure she is not pregnant. This differs from when a man gives a talaq; the iddah period is three cycles or three months.
Is it permissible to delay menses by using medication in order to fast Ramadhaan?
It is permissible for a woman to use medication in order to delay her menses so that it becomes eligible for fasting Ramadhaan, but it is better that she doesn`t do so, and taking the medication is prohibited if she, or her doctors knew that it involves risk on her health. And Allah Knows Best.