Plot number mentioned wrong in sale deed landlord not agree to rectify

Dear sir My mother has purchased a land in uttar pradesh on road 800 square feet in one lakh in 2007 During purchasing landlord mentioned wrong land number of another location (land lord self owner of also another land). But i had forgetton to verify plot number while agreement but after constructed house 2 storey in 2007 on that land then noticed plot number mentioned wrong in sale deed after that we requested to landlord to rectify the number but he dennied and doing blackmail to me to ask 3 lacs Rs and threating me to sell your house to mafia man because your house plot number still on mine name I filled 420, 419 case in civil court and also file case in crime court he went jail for 1 month after he is on bail now got 7 years after his jail . But still nothing happened Landlord says I don't rectify even I gone jail again or giving condition that first quash court case and give 2 lacs Rs then I will go rectify Four way is correct Four way property owner is correct Direct of land is correct everything correct except land number Electricity bill mine name Our few questions please reply all 1- What should I do ? 2- can he sell my house? 3- we are now constructing 3 storey house now can I stop? 4 can you provide best solution ?