You can't quantify something like that with a date. It's like asking "When did God become popular". Suffice it to say that the advent of Greek culture as we know it was sometime around 3500 BC (these are the Minoan and Mycenaean ages... For reference, the Trojan War took place curing the Mycenaean Age, between 1196 and 1186 BC... or thereabouts).
However, none of this was written down until the Archaic Period, around 850 BC, when Homer began writing.
It's impossible for a mortal to become a God
Greek Mythology does not come with a start date.
after the golden age
from the way they had the gods who destroyed the remains of the underworld
They defeated the titans.
In prehistoric time.
She actually was born a Greek god and the rest of all of the Greek Gods.
Cronus
Zeus was not a Greek Hero, but was the King of the Greek Gods. He father was the Titan, Cronus.
They were the religion of the ancient Greeks.
There are none
Isis (Egyptian) Iris (Greek)