But time came when Britain have to leave India, because Indian did not accepted British occupation as their destiny, and kept disputing British right to rule India with their struggle. Britain did not cared but eventually, they had to leave.
You are forgetting some very simple facts here.
British came from somewhere to occupy India. Jammu & Kashmir has no foreign occupiers to speak of. Locals elect their state government from locals, like in all other parts of India.
British did not have ethnic commonality with Indians. The people of J&K share that with rest of India.
British were not Hindu & Muslim. People of J&K are, like the rest of India.
Your comparison is therefore totally invalid. What you are doing is like saying since both water and whiskey come in bottles, they are both good for your body.