1) Even if my mother writes a will and signs off the residential house worth 2 Crores to Daughters ( which is more likely the case here) Will i be able to challenge the will ?
Your mother is not the absolute owner of the entire properties, she can bequeath only her share of properties to anyone of her choice, you can very well challenge the same because you have a legitimate rights and share in that property.
2) Is there a way I can pull back/ withdraw my Co-Obligation status from the bank loan (Because the bank loan is still on my name) , I have tried to convince my mother on the basis ( if I am not allowed to stay in the house, then let the daughters take the loan in their name) but no results , She continues to be pro daughter oriented person :
You cannot withdraw from the bank after availing loan on your name. If you dont pay the loan amount then becoming default in repayment, the bank may initiate recovery action legally including seizing the property through sarfesi act.
3) Are there no benefits given to Son, In cases where Son has taken care of the family after Father's death, got the sisters married taken care of mother ( in terms of all marriage related expenses & medical expenses)
Basically today I stand penniless all my income was shoved in to this home loan, Mom's medical expenses, sister's wedding running the house for last 10 years etc ( sorry I am opening up a lot pf personal things, but I think when the Son has duly done all his duties, Shouldn't law be considering all these ?)
Law is equal and common for every one. There is no question of binding the same for some sentimental reasons. If you had spent for your sisters marriage, that was your duty to do it and nobody forced you to do the same. It is for the sisters to be loyal and faithful for your deeds, but when they dont realise this, you cannot claim them legally nor the law will support your case to show mercy on you on this ground.