21years girl is suffering from brain tumour.please tell me the best doctors or hospitals in india or abroad where success rate is 100percent.

I don't live in India, so I cannot recommend any doctors or hospitals. But you do need to know that with any kind of cancer or tumor there is rarely a 100% cure.

Like J_9 said, 100% is a lot to ask for.
I have a neighbor who was in very serious condition with a brain tumor one year ago. He was operated on at the local hospital and given no hope.
He went to the National Cancer Institute in Bethesda, MD. They removed all remnants of the tumor and now I watch him walk his small children to the school bus every morning. He is not 100% (compared to before the tumor) either but I think he would say he is 100% better (in health and spirit) than he was a year ago.