You cannot imbed Portlets inside Portlets. Just multiple Portlets on a Portal page. It all comes down to the Portal vendor implementation. How can the Portal do the necessary Session tracking, Window state and Mode checking of a Portlet inside of another Portlet. It just isn't in the spec. So if a vendor does allow this, then you are vendor locking yourself.
Yeah we can display more than one portlets in a single portlet application. In a Portal page there are multiple portlet applications will be placed.Each portlet application can have one or more portlets.
1.Say I develop three portlets Administrator,Retailor and Distributer and as per the group and role access configuration can I display only one portlet related to one of them on portal page?
2. Or I will develop only one portlet and use portlet personalization to display by validating against group and role access configuration?
I think 1 will be solution and then I will use personalization at portal page level to not display other two portlets based on who logs in. Please correct me if I am wrong?