I forgot my old phone passcode for again sign in

You'll have to erase the phone using a computer by following the directions here --> If you forgot your iPhone passcode or your iPhone is disabled - Apple Support

This does require you know the Apple ID and Password for the account.

If you do not know either the current passcode, or the previous passcode, I don't believe you will get into the phone, except by resetting it with the aid of a computer. That will erase all of the stuff on the phone. You will lose anything that exists only on the phone (and wasn't, say, saved in an iCloud backup or synchronized to iCloud).

You probably will need to know your Apple ID and Apple ID password to reset the phone.