Has anyone got any idea on this?
Depends how the authentication to your Intranet is done. If it's against something like MSAD then you can just define your SSO against that.
Docs to start from : https://docs.oracle.com/middleware/11119/biee/BIESC/sso.htm#BIESC6044
You'll find information about row level security in the RPD guide here: https://docs.oracle.com/middleware/11119/biee/BIEMG/toc.htm