Property rights of married daughters, property in mumbai

I reside in Kerala, but this is regarding property in Mumbai. My dad owns an office/gala and a flat in Mumbai. He also owned a house/property in Kerala. My mother expired around 32 years back, and my father remarried. Around 2 years back, my father transferred his Kerala property in his second wife's name and informed us later. He had specified that the Kerala property would be for her and the mumbai property for my sister and me. His second wife has 2 sons from her first marriage. She was a widow at the time of remarriage. My dad is 77 now and quite forgetful, but lives an active lifestyle. Now he wishes to sell his office/gala in Mumbai and is planning to settle at his wife's native place. all his property is self-acquired, nothing ancestral. Is there any way we can stop him from selling his property? many years back he had sold his house for around 30 lakhs and brought the current house that he is living in, for 16 lakhs. As to date, me and my sister have no idea where the rest of the money has gone. His wife has complete control over him. Also, do we come under HUF? Is there anything we could do to safeguard ourselves? In case he sells the gala/office and takes the cash along with him to settle in second wife's native place, after my dad's death, will we able to later on question his wife regarding the cash (which should come around 2 crores). If she gets the cash transferred in her account/name can we raise an issue against it?