Transfer of ownership or nominee

Hi sir, I nd my 65 years old dad has been living in a flat in Dombivli thane mumbsi from last 32 years since building was made.frm 1988 to 2014 for 25 years all bills maintenance electricity bsnl all came in my dad name but house name is still in my chachi my dad's own bhabhi name.2014 my bldg became society nd may 2020 my chachi owner of house died in Dubai Chachi has her no own children der is one bro nd sis but dey r chachi s step kids my chacha first wife kids before dying my chachi had filed nominee form which my dad has Xerox but itz not notary the society chairman has misplaced or not giving original nominee form last 3 years now they r harassing my dad to pay 1 lakh rs for deemed conveyance deed nd asking to bring attested true copy of dead certificate of chachi frm dubai nd bring noc frm all blood own Bros sis of dead chachi nd indemnity bond or dey r asking my dad at 65 years age to go court nd bring court order in his name my dad now is very aged he has no income can't even walk harassing senior citizens plz guide me plz