Oc & cc

Dear Sir, We are looking one flat near hosa road, Bangalore. which is having BBMP approval with A khatha ( for land only flat will fall in B katha). Builder is refuse to give the OC & CC . he is saying that around 10-15% deviation are there, also its only G+3 with 20 flats are available hence he cant provide the same. but he is saying in that area 99% of builders wont provide oc & cc. but how ever he said during akrama- shakrama we can get transfer to A Khatha by paying batterment charges. Building under construction and it may take another 6 months to position. fyi national banks & LIC is providing loan for that. 1. is it advisable to buy the flat? 2. if we buy that, can we apply for akrama - sakrama ? and what types of documents are need for that? 3. how much % for betterment charges? and if suppose we got A khatha is it ok or still we need OC & CC. 4. can we resale the flats with out OC & CC? 5. how much dangerous to buy this type of flats and to they punish severely ? Kindly advise me in this regards.Thanks in advance