Will

My brother has forced my father to sign a document(On a stamp paper) for the house he lives in, he did not give any copy to him hence I am not very sure what is the document. As per my father it is a divison of the house as he takes ground floor of the property where he partially has office now and rest area my father lives in.He is also staying in the property on first floor which will be my part as per my father. 1) What can be the authenticity of this document and will that be challengeable by me, my sister and my mother? 2)Can the above document be a gift deed? Can my brother make it legally valid now and my father can't do anything now. As of now my father has not helped him get it registered though. Can he get that registered by himself? 3) Can my father make a will favorable to all and get this registered , He has a neuro desease for last 2 years and has difficulty writing legiblly and signing as well. 4) Can he make different gift deed for his properties against 3 joint owners? 5) As He is staying on the first floor which may be mine. Can he refuse to vacate for me and continue to use his office on ground floor as well?