Complex gpa questions

Hi Sir, I have few questions on GPA vs SPA. Can some one clarify it please. I'm trying to look at a house which is under construction. The history goes like this. 1950's Person1 got the land of 2 survey numbers for example 1 and 2. 1 has 1 acre and 2 has 2 acres of land. In 1990's Person1 passed away. In 1994 Person2 and Person3 are sons of Person1, Person4 and Person5 are sons of Person2 (all 4), executed a registered GPA to 2 people, called GPA1 and GPA2. In 1996 GPA1 and GPA2, They both made a layout and sold the plots. Two of the plots say site numbers 26 and 27 (40x60) were brought by SiteA and SiteB. Later in 2004, These 26 and 28 brought by same person and he was the GPA holder of his daughter in abroad. In 2007 Person2 passed away and Person2 wife, person3, Person4, Person5 and rest all of the family did a sale deed of Survey numbers1 and 2 to other people. Later in 2008 Person3, 4 and 5 revoked GPA. Here the question is without revoking GPA, Sale deed happened for entire 1 and 2 survey numbers? Is it valid? Later in 2019, Person in abroad gave a SPA to sell both sites, and SPA holder sold it to builder. and builder is constructing the house now. 1. Property was sold by SPA holder, will original owner has any right in future to question the property? 2. All GPA and SPA;'s have register office seal and sign. How can we validate they are right? 3. As per GPA act 2011, if there is no sale deed the GPA is invalid. Does it apply to the people who took GPA in 1990's and form the layout? 4. In 1990's Person1 5 daughters didn't sign on GPA / Sale deed? Will they have right to question now? Please clarify; Thanks.