How can you identify a Hindu?
Almost all Hindus wear tilak/bindi/kumkum - A decoration, often a red dot, traditionally worn on the forehead.
I believe that is probably the Hindu relgion. There are literally millions of gods in the Hindu faith, so many that no Hindu could possibly be able to identify all of the gods. As I understand it, each family even has their own patron god. further Hinduism is known as a polytheistic reigion, because it has many gods.
The Upanishads are a collection of more than 200 philosophical texts of the Hindu religion. In the same way that the Torah, Bible and Qur'an shape the Abrahamic faith's sects, the whole of the Upanishads shape the Hindu religion through canonical statements. It would be difficult to identify the beliefs from them without quoting them in their entirety.