Hi anonymous user
Q1: How to make these users automatically register to application on registration/login.
You need to create the signupsignin user flow in your Azure AD B2C portal, then select Run user flow in the portal. For Application, select the web application named ProxyFramework that you previously registered, then click on run user flow and select Sign up now. Refer to the official doc.
Q2: I have some users who are registred to the App. But when I try to change passwords for them, it shows Insufficient Privelges. I have given almost all permisions.
Modifying passwords of B2C users using application permissions is not supported, you should grant Directory.AccessAsUser.All
delegate permission for your application and grant admin consent, then use Azure AD based authentication flow (eg: auth code flow) to get the token.
Finally, you only need to modify the password in the passwordProfile field.
If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".
Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.