Question on New Fine-Grained Security Features

1. Is it possible to have a default log-in so that the public is not constantly asked to enter a username and password?

2. With the proxy server blocking access to the REST API, what happens if I choose to host layers on ArcGIS Online? Will individuals be prompted for passwords or am I circumventing the security by listing the un-secured REST API instead of the proxy?

Thanks for the feedback.