Is washing both openings (Istinjaa`) a must before every ablution?
Washing the front and back openings (Istinjaa`) is a must in case they have an impurity, but if they do not, there is no need for that, and Istinjaa` is not a condition for the validity of ablution.
Is it permissible for a father to divide his property amongst his children except one under the pretext that he has paid for the latter`s tuition? This is knowing that his other children were given the opportunity to pursue their education but didn`t because they were educationally poor. Moreover, is he allowed to give his other children who have helped him with growing his business?
All perfect praise be to Allah the Lord of the Worlds. May Allah`s peace and blessings be upon our Prophet Mohammad and upon all his family and companions.
The father should be just between his children as regards gifts, in case they had similar circumstances. However, if any had a special merit, then it is permissible for the father to take that into account to be just. For example, giving his children who have helped in making his fortune and received no reward for that or giving the little ones because they haven`t taken as much as the older ones or giving the sick child who is unable to make a living. The most important thing is achieving justice. Moreover, the father is not interdicted by any of his children, and he is free to do whatever he wants with his money and Allah will call him to account as regards observing justice between his children. And Allah The Almighty Knows Best.
What is the ruling on a man leading his sisters in obligatory prayer, or Taraweeh prayer (Night prayer in Ramadan)?
The prayer of the man who leads his wife, or sisters in prayer is valid, but it is more rewarding for him to offer obligatory prayer in the mosque. And Allah Knows Best.
Is it obligatory for a wife who has been abandoned for many years to observe the waiting period (iddah) after her husband passes away?
If her husband passes away, the wife is required to observe the waiting period (Iddah), even if he had abandoned her, because she is his wife and inherits from him, so she must observe the iddah after his death. And Allah Knows Best.