Change in ownership of the builder and promoter

Dear Sir / Madam, I have purchased an apartment (under construction, but near completion) in the year 2012 and the said apartment was due to be handed over to me by June 2013 as per the "Agreement of Sales". Till now I have maid near to 80% of the price, the said apartment has not been handed over to me, I received a letter of completion and upon visit to my apartment, I found that work was going on and it no way could be called completed. After that the company (builder) from whom I purchased the flat, has sold it's entire stake to some other group. I have received no official letter from the new company who has acquired the (old) builder. I just received one email, that too when I visited the correspondence address given in the "Agreement of Sales" I found nobody there. In this context I would like to know that there has been considerable amount of delay from the builder, the said builder has sold it's entire stake, the apartment is NOT yet registered to my name, does any law allow me to force the new company to give me an option to come out of the said "Agreement of Sales" and make them pay the marketable interest on the amount that I have already paid to them. Thanks.