`node-oidc-provider` with Email verification

Question

I'm creating an OIDC provider with oidc-provider. For now, my Registration flow required email verification step, which is handler outside oidc-provider. This approach works but it leads to an issue that user can not automatically login after setting up their password.

I thinking of creating a new prompt policy name email-verification, something like:

https://<auth-endpoint>?client_id=...&prompt=email-verification

I wonder:

1. Is this flow acceptable with OpenID Connect specs?
2. Is there any document, tutorial or example in terms of specs or implementations of this approach?
3. The case user register in mobile app, but open email link in web (we have a mobile app with different client_id and of course, different redirect_uri. What should we redirect user to the app without error.

Thanks,