Unregistered sale agreement validity & limitation

I sold a piece of agri Land for Rs 55lacs & entered into "Unregistered sale agreement" on 1000 rs stamp ( 100x10) on July'2017 . Token money paid was Rs 51000 & I never met buyer & witness & blindly signed agreement wit my initials. Buyer husband was known to me & he ave criminal background & he smartly put a claise that i have given him possesion whereas actual posession is wit me till date & on revenue record too . As per agreement buyer was suppose to get registered land on her name after paying balance amount of 54.5 L before 31/03/2018. But he failed & never responded in spite of my numerous calls/ SMS/ Wts up msgs to her husband as I didnt knew agreement was on her name & husbamd had purposely not given copy of agreement after signed by is wife. He serve me notice on 05/03/1021 for accusing me of not fulfilling t&c of agreement & get property registered . I did replied through my advocate ,denying is false accusition& claim . He filed a suit later in session court after paying Rs 150000/ court fee .I recieved summon on 6,March'.2022 . please advise : Can She file suit without paying stamp duty on unregistered sale deed? can shhe file suit even after such a long time. Can she claim land, as she defaulted agreement & never turned up foe registrationn before due date 31/03/2018 inspite of my numerous reminders before time. I did land measurment as per is demand & agmnt clause before due date in presence of his representative who signed on all givt papers & panchnama as witness.