1) First you need to apply for register your name in the local gram panchayat office along with all papers like land papers, which are on your grandfather's name, fathers death certificate and other uncle's death certificate, domicile certificate etc.
2) Not needed, first you can register mutation record on your name i.e. all legal heirs and directly you can take objection.
3) Within 3 years you have to register your objection from the time of incident took place.
4) Yes, later on you can file defamation case, first get mutation papers on your name ready.