Question Regarding Deviation

[DenQuest]

I am in negotiation phase with a builder. While going through the approved plan , I came to know that the approved plan is for around 1000 sq.ft. and the actual buildup is around 1650 sq.ft . When I asked about this to the builder , he said it is a common practice in Bangalore and it is impossible to build as per the government regulation , etc etc..

I would like to know , what all are the legal complications if I purchase this apartment?

Additionally , the approval for the building is for G+4 and builder has done a 5th floor without approval. The apartment I am interested is in 1st floor. So the 1st floor apartment should ideally not have any legal issues from vertical deviation isn't it?

~DenQuest