Sixteen sayyid amal

Q: I have heard about an amal called 16 Sayyid in which we have to make only one dua as the main target for 16 months and we have to pray every prayer compulsary on the 16th of every Islamic month and have to fast on that day.

Many people claim that on doing so their duas have been accepted and I am also evident of that. Could you please tell me, is that authentic and can we do that amal?

Inheritance

Q: If a woman passes away and leaves behind her son, her mother and brothers and sisters but no husband and father. Who will inherit and how will the shares be divided?