Mother of unsound health cannot sign will.

My mother is Bedridden, Unsound and cannot sign.She is sole owner of the property with no will. I am only child of my parents. I want to clarify following queries -

1) Can i take loan against property in which my mother is sole owner as she is unwell with no will can my father sign on my mother behalf to avail the loan.As bank required Co-applicant to sign and my mother is not position to sign?
2) If i want to sold the property while she is still alive how can i do?
3) Do i need to give NOC to my father?
4)As said im the only child so no one will be their to challenge the will .Is will with thumb impression of my mother will valid?