Which is the fastest growing religion?

Islam is the worlds second-largest religion, after Christianity.

Who was the first known God?

Inanna is among the oldest deities whose names are recorded in ancient Sumer. She is listed among the earliest seven divine powers: Anu, Enlil, Enki, Ninhursag, Nanna, Utu, and Inanna. These seven would form the basis for many of the characteristics of the gods who followed.