Hi. I need to learn more about Hinduism, I don't know nearly enough about it. But a Hindu is someone who considers themselves either culturally or ethnically Hindu.
Yes. They consider themselves Hindu and they are also Buddhist for religion.
In history, the word Hindu has been used to identify people from South Asia or whose cultural identity is in South Asia.
Yes, but essentially those who live in the Indian peninsult.
It's unclear how Hindu self-identity developed in local populations to South Asia, in the religious and cultural sense.