Netflix emailed me many NetflixHelpCenter articles.

— 6-digit service code .. If you don’t know your email address used to register the account, then you may use the service code.
— password.. Hotline told me I can change password any time. There is only one password and one email address for the entire family. When I change password, I have the option to sign-out all devices.

IFF a device is not signed in, then I need to sign in for that device. This sign-in process uses THE email address + THE password

— profiles

The first profile listed is the main profile. All other profiles are regular profiles.

Each profile can have a profile lock. I don’t like such extra complexity, so I removed profile lock on the main profile.