Is The Suit Barred By Limitation.

My grandfather had 6 children including my father. A house was purchased by my father in the year 1989 in the name of my grandfather. My father was GPA. My grandfather died intestate in 1993. In the year 1995, my father sold the property to my grandmother (without RD from other legal heirs), and my uncle(chacha) was given the GPA. In 1997, my grandmother got the property freehold from DDA and became the absolute owner. After that in the year 2000, she gifted the property to my father through a registered gift deed as the property was purchased by my father's money. After 18 years, other legal heirs of my grandfather took advantage of my grandmothers deterioting mental condition and convinced her that the property belongs to all the legal heirs and that my father has fraudulently got the property transfered his name. Now, my grandmother has filed a property suit against us claiming that she is illiterate and mentally ill and had no knowledge of the execution of the documents. Now seeks cancellation of the documents(gift deed, conveyance deed and agreement to sell). The documents she has submitted in the court consists of certified copy of gift deed only, and photocopies of conveyance deed and agreement to sell is attached. Can we prove that she was in possession of the documents from the beginning as photocopy of conveyance deed is attached and prove that the suit is barred by limitation.