Khata 'a' available for layout but not for individual site

Hi, I am planning to purchase a plot in an Unapproved Layout situated in North Bangalore, While Field, Hagadur Village. The owner says, that Title is clear, layout is 'A' Khata and sites are B khata but the layout is unapproved. Can any one of you please clarify my questions: If I purchase a site in such a layout, can I convert it to A khata. Will I get any problem in future if I don't have A khata. If others in the layout wont convert it to A khata, what will be problem. How can I convert it to A khata. Please help me in taking a decision by resolving my above queries. Thanks a lot !!!! Thanks, Sreenath