Their parents made bequests before they died stating that the estate was to be divided in a specific manner; do they have to follow that?

If he dies and does not leave behind anyone but a brother or sister through his mother

He agreed with his father that he would pay the Hajj expenses for his mother, then his father died before he could take her

She died and left behind a husband, children, a full brother and a half-sister through her mother

She died and left behind a husband, three sons and six daughters

If the fiancé dies before the marriage contract, does his fiancée inherit from him?

He died and left behind a mother, a wife, a son and two daughters

The father did not divide the estate in accordance with sharee‘ah and he deprived his siblings (of their share of the estate); do they have to re-divide it?

Inheritance of properties

If the mother inherits from her deceased daughter, then the mother dies, does what she inherited from her daughter go back to the children of that daughter?