does Azure AD B2C provide one endpoint like user-info-uri from OIDC for each sign-up-or-in policy?
Solution 1:
As of now, Azure AD B2C does support the user info endpoint only through the Custom Policies.
If you are using built-in User-flow policies, then you will have to set it up yourself and hardcode the library to look at your custom endpoint. All the endpoint needs to simply do is read the id token, validate it, and then return the claims inside in a JSON format.
There is a feature request for this, on Azure AD User Voice.