Self acquired property with Unregistered will

Hi, My father has expired in month of FEB 2013 and he has left behind his self acquired property (one agriculture land "A" purchased in 1972 and one home "B" purchased in 1984 both were on his name at the time of his death). And there were one more land "C" he purchased directly in myself, brothers and mother name (we all have individual sale agreements registered in year 1996) After my father death property "A" & "B" are transferred to my mother name in 2014 ( there was objection from my sister, after hearing from both side Tahasildar allowed to transfer "A" to my mother name, and "B" transferred without any objections) Now my sister filed suit and sent notice stating that land "A" is ancestral property and she is also co-parceners for both "A" ,"B" and "C". After getting notice from my sister, I started searching property "A" sale agreement document which is missing now, but I found the Old RTC were in the year 1971-72 seller name is there and next year i.e From 1972-1973 onward RTC's are in my father name (Till 2014, after my mother name is there). And I also found one will written on Stamp paper in the year 1987 and signed by 2 witness. one of the witness is alive and other is not alive. My questions are Can I produce only RTC's for Property ''A" to prove that it is not ancestral property? is there any other document I have to collect it from govt office. (it is purchased in year 1972, as mother told). Can I use Unregistered will to prove my father wanted to make property in mother , brother and myself name, how to get probate it What will happens to property "C"?? thanks in advance for your advice.