insurance or will

In case of Insurance, Nominee only is the preference to get share

You are mixing up the issues. As far as insurance claim on her death, the nominee receives the money, as he is intended to be the beneficial nominee.

As to other assets, if mother died intestate ie without writing a Wii, all legal heirs shall have equal claim.

The mother has every right to give her share of the property to any child as he likes through a will.  If there is a will, other children can not challenge the rights of the nominee and it strengthens the title of the nominee to avoid legal complications if any from others in the future.  So registering a will in the name of the nominee is essential.

My advice would be that your mother should write a Will mentioning your share and daughter's share therein giving full details in the Schedule. Since you are the nominee for Insurance policy, although you shall be getting full amount, nothing wrong in mentioning about LIC policy also with full share in the Will.

Unregistered Will is a valid Will and registering the  will is optional. To avoid delay in getting the Will Probated etc it's better to get it Registered. In case your mother writes another will subsequent to the Registered Will, the latest Will only shall be valid even if it so happens that it's not registered.