Hi friends. I am 252116211. You may think I am 252116211 or 252116211. But I am not. Also, I am not 252116211, 252116211, 252116211.... or some other 252116211. There is a lot that's not what I am. I am lazy enough to list them all. But one thing I can guarantee you, I am definitely 252116211. If you know the old bda, who expanded his three member family to ten by inviting seven new members, with his help, you can find me.
Tell me who I am and how did you find me (it will be appreciated if you can explain everything mentioned in the question).