This is completely untrue. In some parts because of intentional acts and in some parts accidental acts.

The most commonly held understandings of "the devil" by Christian groups are not sourced at all from Biblical sources. But here's some correct information...

The number of the beast is 666, because the beast is a legion of demons that number six hundred and sixty six. Which... numbers are symbolic, so 6 times 6 times 6 doesn't actually mean 666, it just means "a whole lot of evil". A legion of demons are demons that have either taken on the same host, or have united in power to become one being despite their individuality. They can split up or stick together.

This comes from Old Testament times, where it is believed that all other gods besides Yahweh are lesser gods and evil, therefore demons. And therefore Yahweh is the one true God.

Lucifer, The Devil and Satan are all individual/different things/concepts/whatever. Lucifer is a fallen angel, sent to keep bad guys in hell, because he defied God. But angels don't have free will (which was why God created man, allegedly) so if Lucifer defied God, it was because God commanded him to. Which... doesn't quite make sense. Lucifer is supposed to be a good guy jailer who has to be in hell because someone has to guard hell... but over the years the various churches have invented the concept of "the devil" and merged it with Lucifer and the great satan, incorrectly.

Speaking of, Satan isn't a guy. Satan just basically means "evil" and "the great satan" just means "the great evil". It refers to the sum of demons, that exist, which will someday form a legion together and become "the beast" as we know it.

Some of this came up over time due to incorrect translations. Some from wrong teaching. Some from trying to simplify teaching to dumbdumbs, back when people lived in huts as farmers and couldn't really understand most concepts we do today. But the lack of official correction for some of these understandings and teaching about satan, the devil, evil, Lucifer is overdue.