Custom Amplify & Cognito Authentication

I would like to create a web app that authenticates just as AWS does for console login.

1. A non-root user would first have to enter an account number (I can verify that the number entered is legit).

2. The non-root user would then enter an email and password combination. That alone is ok, but I don't see how to confirm those credential using Amplify in combination with the account number. I only want the user confirmed if those credentials are paired with the account number.

3. For root users, I would want to authenticate them only if the email and password can be confirmed with, presumably, a root user flag.

Is there an Amplify API that allows email, password, and account parameters for authentication?

Can you provide any guidance on how to authenticate root users based on email, password, and root user flag? Thanks.