Is it permissible to repeat the Istikhara (seeking guidance) prayer, and is it a condition that one should sleep after offering it?
All perfect praise be to Allah,The Lord of The Worlds Istikhara is offered once, but it is permissible to repeat it, and sleeping after offering it is not a condition for its validity. And Allah Knows Best.
Is Aqeeqah due on the miscarried embryo?
No Aqeeqah is due on the miscarried embryo.
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.
A man has raped a woman and she gave birth to a baby boy. To whom should that baby be attributed?
All perfect praise be to Allah the Lord of the Worlds. May His peace and blessings be upon our Prophet Mohammad and upon all his family and companions.
First of all, the adulterer must be punished according to the rules of Sharia and the baby isn`t attributed to him. Rather, it is attributed to the mother. This adulterer has committed a grave sin and incurred the wrath of Allah. We advise him to make sincere repentance to Allah and pray that Allah forgives him. And Allah The Almighty Knows Best.