Neither the Ancient Greeks (Plato, who wrote down the legend, was Greek), nor the Ancient Egyptians - who reportedly were the ones who told the myth to Plato during his trip to Egypt - believed in a single god. Their Pantheons had numerous gods, so I would say "No" in answer to your question.
No, natural disasters did.
the reason why Poseidon sunk the city of Atlantis is that the people were so sinful that made Poseidon very angry and sent a tsunami to sink it...
The year 9600 BC.
No God lived on Atlantis. Atlantis was ruled by twelve kings who all died when the island sank. After that nobody lived on or even in Atlantis.
Atlantis is a semi-mythical place. There is no evidence that it really existed. If it did it was likely to be in the Mediterranean Sea.
He was the sea god of Atlantis.
Correct.
Atlantis is not a God but Poseidon's first born child's name was Atlas so the Empire and the surrounding ocean was called atlantis
Its possible maybe Neptune the Greek god of water perhaps was punishing the people of Atlantis for something they had done or was jealous of how beautiful the island of Atlantis was or they were punishing them for how they were using gems and crystals they were using to control everything. Or maybe Zeus made a storm and killed the city.
Atlantis was the domain of Poseidon, the god of the seas, storms and earthquakes.
In Roman mythology, there isn't a specific god of Atlantis, as Atlantis is primarily a story from Greek philosopher Plato. Atlantis is depicted as a powerful and advanced civilization that ultimately fell out of favor with the gods. However, if we consider the Roman pantheon, Neptune, the god of the sea, might be loosely associated with Atlantis due to its maritime themes. Nonetheless, there is no direct Roman representation of a god specifically tied to Atlantis.
According to Plato, 11,000 to 12,000 years ago.