All religions spread by word of mouth to some extent. They also spread through conquest and power.
Just because a conquest is unconnected to religion/ideology doesn't mean it doesn't help spread it.
You asked about Hindus and slavery. I gave an example.
Do only Indian Hindus count?
You defined modernity as progressive, what did you mean by progressive?
In your opinion what defines modernity?
Indian, Chinese, etc religions didn't use power to spread. In fact the Abrahamic faiths took much of the ancient Hindu empire like Philippines, Indonesia, Brunei, etc by scaremongering and bloodshed.
There is no evidence in history that Hinduism showed any form of radicalism before the British raj in India.
Yes, only indian Hindus count as Hindu simply is the Persian pronunciation of the people who inhabited the plains of Sindhu (river) and Saraswati.
All the major histories took place in India including the birth of the Vedas and the great war of Mahabharata.
Modernism- bringing things upto date based on the views of majority.
Progressive- something that changes and is updated with time.