I just restored my iPhone because i lost the passcode but messages ask me for old passcode

You have multiple devices that is either using the same Apple ID or had used the same Apple ID in the past. You would know the passcode unless you had shared your Apple ID with someone who cannot be contacted now.

That is why it is recommended that Apple ID should not be shared.

Now the only option is to log into https://appleid.apple.com with your Apple ID credentials and remove all unknown devices.