The Greek gods typically turned into things having to do with nature - mist, mountains, trees, rivers - as the Greek gods and goddesses were born of nature (Gaea: Earth), but they could also become animals such as cows, deer, horses - which they were in some way connected with, or which were sacred to them.
No they did not the gods were the most important things ever back then
Many Greek gods go into disguise when interacting with mortals. Zeus often had love affairs with mortal women and often disguised himself. When the Greek gods wished to test mortals, they would disguise themselves as well, for example in the myth of Baucis and Philemon. Sometimes the gods disguised themselves as mortals, and sometimes as beasts.
The gods created fire, but kept it for themselves. Prometheus stole it from the gods and gave it to the humans.
The Titans existed before the gods and were more powerful.
Because they were gods so they did what they wanted and the Greeks probably felt less guilty about themselves being messed up if their gods were also.
Greek mythology has more than three immortals, the gods themselves were immortal, such as Zeus, Hades and Poseidon.
They call themselves Neopagans, though they usually follow Norse mythology more often than Greek.
Greek monsters were truly monsters that humans feared. They were large and had animal parts. Some were also part gods.
acording to Greek mythology, "Zeus (king of the gods) crafted a weapon stronger than the the gods themselves and killed his father Kronos (the Titan lord) and banished him and the rest of the Titan's to the pits of Tarturus to be forever shackled in there torment".
The Greek gods are laws unto themselves, so sleep or not is likely, as there was a god of sleep.
No, the Greek gods are myth.
Yes, the Greek gods are immortal.