Power BI Premium Admin Portal in multiengagement organization

Hi,

I'm just after today's webinar and have question about Admin Portal.

I expect my organization will buy PBI Premium. One P1 for the beginning.

1. Who will be the admin of Admin Portal?
2. Is it possible every Engagement (Project, 100-500 users, separated content, security, client) will have his own Admin Portal or something with similar options?
3. I don't want to request one Superadmin for every change. I want to manage it by myself, inside my Engagement but also as part of one PBI Premium P1 (for example). Is it possible?
4. I compare it with SharePoint. Organization has license for SharePoint, but every site has his own Site Collection Admin. Is similar option possible in Power BI Premium Admin Portal and what I've seen today on webinar will be available there?