Is unregistered sale deed validated by district registrar valid??

I have entered the agreement of sale for the newly Constructed House in Hyderabad and gave advance of 1/4 th of the sale consideration. Here the problem is Mr.A Converted the agriculture land into NALA in 1984 by layout of plots . Mr.B purchased the plot from Mr.A in 1985 and executed the sale deed ,but the same sale deed was not registered in SRO. In 2007 Mr.B sold the plot to Mr.C through a Registered sale deed at SRO, but two days before the registration,the Sale deed between Mr.A and Mr B was presented before the District registrar and Collector. The same document was Validated under section 42 of Indian stamp act II of 1894,Vide file No 1560/AR/2007 in District registrar and Collector by collecting deficit stamp duty together with penalty. In 2009 Mr.C sold the plot to Mr.D through a Registered sale deed, In 2012 Mr.D sold the plot to Mr.E through a Registered sale deed, In 2019 Mr.E sold the plot to Mr.F through a Registered sale deed, In 2021 Mr.F sold the plot to Mr.G through a Registered sale deed, In 2022 Mr.G Constructed the house by taking G+1 permission from GHMC. Now I entered the agreement of sale with Mr.G (present owner). (1) Is unregistered document b/w Mr.A and Mr.B validated by DRO valid? (2) Tittle flow from Mr.A to Mr.G( present owner) is clear? (3) All the registered documents are reflecting in EC except unregistered validated document b/w Mr.A and Mr.B . what is the reason? (4) can I proceed with further process of sale or not? Thank you in advance for considering my question.