Old Apple ID stuck in icloud field

I deleted an old apple id email and do not have the password associated with the account anymore

(a) On my iPad, under icloud is my old Apple ID/email address. I am unable to enter a new Apple ID/Email. How do I enter a new Apple ID?

(b) On my iPad, when I attempt to put my Apple ID and password in Itunes, it tells me 'Cannot connect to iTunes store

(c) On my Macbook Air, I am able to sign in to my icloud account with the correct Apple ID/email

(d) On my Macbook Air, I am able to sign in to my itunes account with the correct Apple ID/email

(e) I attempted to sign out of my icloud account on my ipad air but it asks for the passcode which I no longer have

(f) I am unable to erase all content and settings because it is asking me for the password associated with the old apple ID/Email

Please help