Kashmir was originally independent at the point of independence from the British Empire. Before that India simply wasn't in the same state it is today and existed in various different shapes throughout the ages.
The existence of Bharat Varsha in the proportions claimed is not a broadly accepted historical claim, it is a concept linked to Hindutva.
Oh sure it does, because Hindus and Muslims were getting along just fine before that right, with the Mughals and all?
You can't blame everything on Britain I'm afraid.
At least we have a free press and independent law enforcement and judiciary, plus a democracy. That keeps some semblance of truth.