Is it permissible for the big brother to force his sisters to wear Hijjab (Islamic wear) if their father didn`t do his part in this regard ?
All Perfect Praise is due to Allah, The Lord of The Worlds
The father`s attention should be drawn gently and politely, and the sisters should also be reminded with good words since Allah, The Almighty, Says (What means): "O ye who believe! Save yourselves and your families from a Fire whose fuel is Men and Stones." [Al-Tahreem/6]. And Allah Knows Best.
Is Making up Missed Obligatory Prayers an Obligation?
All perfect praise be to Allah, The Lord of The Worlds, and may His peace and blessings be upon our Prophet Muhammad and upon all of his family and companions.
Missed obligatory prayer/prayers is a debt upon Muslim and making it up is an obligation, since the Prophet (PBUH) said: "pay the debt due to God, for it is the one which most deserves to be paid." [Agreed upon]. And Allah Knows Best.
Is it permissible for a wife`s family to demand her husband to divorce her although she doesn`t want that?
It is forbidden for them to do that in case their daughter doesn`t want divorce unless there was a sin that continues as long as the marriage survives.
A person owns sheep or goats and occasionally feeds them from the grass in other people's orchards without the owners’ permission. Is it permissible to eat the meat of these animals if invited to do so? Is it permissible to purchase from these sheep whose owner feed them from people's orchards without their permission, and can one accept gifts from them, such as meat or milk?
Yes, it is permissible because the one who is accountable is their owner, and the cost of the grass on his accountability. In addition, in order to be on the safe side you should abstain from eating his products, because his sheep case is as if they were fed on impurities. And Allah Knows Best.