Property bought through GPA in 1987

Hi, I am planning to buy a plot in Hebbal, Kempapura area of Bangalore and need some advice . This plot was originally part of 4 acre land that originally belongs to a lady by name Muthamma. She had sold this entire land to a person by name Raju through a registered sale deed in 1966. Raju has formed smaller plots in this land has sold them through a notarized GPA (not registered) in 1987. One such plot has been bought by a person named muniraju 1987 (through a notarized GPA (not registered)). Within a span of 11 months, in 1988,, Muniraju has sold this plot to a person by name Ramesh through a registered sale deed and Ramesh has sold this to another person by name Vijay in 2009 again through a registered sale deed. I am now planning to buy this plot from Vijay. This is not a DC converted land but Vijay has got a BBMP , A khata issued in his name by paying betterment charges. I have checked encumbrence certificate from 1989 till and that shows transactions happened between Ramesh and Vijay and latest EC shows Vijay as the owner (no encumbrence). However when I look at the latest RTC for the entire survey number( 4 acre land), it has gor Raju's son's name on it. It appears from RTC that he has got khata done in his name for entire 4 acre in the year 1996 . I seek you advice on the following 1. Do I need check the encumbrence certificate for pevious years (before 1989), if yes for how many years do you suggest? 2. I am concerned about the initial GPA transaction that has happened between Raju and Muniraju. Eventhough all the subsequent transactions have happened via registered sale deed, I would like to know wether there will be any problem in the future because of that first GPA transaction.? 3. The latest RTC has Raju's name on it. What does this suggest and will there be any issue because of this? 4. Your opinion on the title of this property? Is it safe to buy? Is there any possibility of legal hassle wrt title in the future ? Kindly advise