Answer
You cannot sign out of or delete an account without knowing the password. That’s basic account security. So you will have to recover the account and reset the password first. The device is an iPhone 4 with iOS version 7.2
Delete iCloud account without Password – any iOS version – iPhone 8, 7, 6S, 5S, 5, 4S, 4
Delete iCloud Account Without Password
How can I delete iCloud from my iPhone without password?
You cannot sign out of or delete an account without knowing the password. That’s basic account security. So you will have to recover the account and reset the password first. The device is an iPhone 4 with iOS version 7.2