It could also mean that Aryans adopted some aspects of Harappan civilization, and made them a part of their lives.
There is no such thing as "Aryan".
Interestingly, this term "Hinduism" for a religion did not exist before Muslims arrived from Iran and Afghanistan. But that's for another thread.
Wrong, Persians only used the term Hindu to describe the people who lived at the Indus Valley. It wasn't used to describe people of a certain religion. The first people to ever do that were the British.