I need to get my old Yahoo Id address back , how do I get it back, I made a mistake wanting another Yahoo mail ID and it took my old one

First its not a good idea to piggyback your question on someone else's. This can lead to confusion. You should start a new thread. So I've moved your question to its own thread.

Creating a new account shouldn't affect an existing one. When you log into Yahoo, if it automatically opens the new Account there is a link for I'm not xxx. Click that and you get to a login screen where you can enter your other account info.