I posted an update to my original answer with additional information in relation to your previous comments. From your summary above, it seems that the upgrade part of your question was somewhat motivated due to the need of the usage of redirect rules and the lack of support for it with the current approach you’re using (Auth0.js 7 - /oauth/ro).
Would you mind posting this as a new question? If your goal is to use redirect rules and custom login pages, then it’s best to start fresh with a new question just focusing on the requirements.