- NoC should be required from father and daughters for mutation if you are not filing for probate and proving the will. You should consult the concerned tehsildar to know about the requisite documents for mutation.
- Even if that family member is unavailable or uninterested in mutation but the mutation will be done including his name as well (as per the joint will), unless he gives up his rights and interest completely in the property.
- Yes, even registered will can be challenged in the court of law by any interested party who doubts the genuineness of the will. So, the objections can be raised against the registered will also.
- Generally, a surviving testator can't alter the joint mutual will as it is irrevocable. In your case, your father (surviving testator) may not alter the joint will pertaining to the property solely belonging to your mother, whose last desire is as per the will.
- Probate is not a necessary mandate but it is always advised that to get it probate done to avoid any future disputes or claims pertaining to same.