Issues with apartment taken on lease

Dear Sir / Madam, We have taken an apartment on lease for 15 lakhs (with 2500rs as maintenance) in Bangalore and have been residing here at this apartment for around 3 months now. However, we have come across some not so good information that builder has taken an loan on the apartment and has defaulted it, which we were not aware off nor he had mentioned about this to us. Around a month back people from the bank had walked into our apartment and we were made aware that the builder has defaulted the loan amount. They said that we need to vacate the apartment within a week as they would be selling this. We did say that we have an valid lease agreement and this wont be possible. They dint turn up after that. When we enquired the builder said that already time is taken from the bank to repay it and there is no trouble. But he has been a big time liar repeatedly which we realized only after taking the apartment. Now we have also heard that this builder has registered the same apartment in the name of his mother and has taken another loan on this. But the lease agreement we have made is in the name of builder and registration was done to her mother is after the date of our lease agreement. So have few queries on this, would appreciate if this could be answered as I assume this builder looks fraud. 1. The agreement as suggested by builder is done on an 200rs stamp paper, would this be valid? 2. The agreement is of 4 pages and builder has signed only on the last page. But he made me to sign on all the pages and said that apartment owner(LESSOR) is supposed to sign only on last page, does this hold good since I doubt his intensions? 3. Will this loan taken by the builder on the apartment affect us or are we legally safe? Our hard earned money which we have been saving for years to get away from rent and buy an lease home is at stake. Could you please guide me on this and let me know how to proceed further. Thanks in advance!!