Migrate Apple Sign in Users from one developer account to other developer account

Hello,

We are planning to migrate our App from current developer account to another account. As our app is using Sign in with Apple, we have to migrate user scoped identifiers from current employer to recipient account. As I was reading articles on developer site (https://developer.apple.com/documentation/sign_in_with_apple/bringing_new_apps_and_users_into_your_team)

My understanding regarding migration process is as follow:

1. Generate Access Token (we didn't stored user access token) using sender details (client_secret)

2. Generate Transfer_sub using above access token and save it

3. Transfer App and accept it on recipient side.

4. Generate Access token for recipient (using recipient client_secret)

5. Generate team scope identifier for new team using previously generated transfer_sub and above access token and update older identifier with newly created identifier in our own database.

6. Use new identifier for future requests. 

Regarding above, please answer following queries:

1. Please confirm me if my understanding regarding migration process is correct as I documented above?

2. Secondly for all the users who have signed up before this migration, if I generate new scoped identifiers for them, it will work for them without requiring them to sign in with Apple again? Otherwise asking users to sign in again would be painful and we might lost users.

3. All of the users who signed up after migration, for them normal sign in flow will work (getting access token from apple sign in and getting identifier from apple as it was working before migration)? These identifiers will automatically be associated to new developer account?

4. I have tried following apis (generate access token, generating transfer_sub) and they are working fine, but when I run api to generate new-scope identifier for recipient using transfer_sub, it failed with error (invalid_request). So my understanding is that, I can only generate new identifier for new developer account only  the app will be transferred?Please confirm me this.

Kindly respond to all of above queries as there isn't good documentation available on internet. So we want to be fully confident in this process from our side before app migration.

Thanks