I am completely new to WP multisites and would like to get

I am completely new to WP multisites and would like to get a few things clear.

Is this possible:
I want a main site with a blog. And every subddomain needs a blog of its own.

When I make a post on the main blog, is it easy to place this post in any (not all) of the blogs at the subdomains?
And can this be done by the super-admin alone, or can an admin of one of the subdomains post this blogpost on its own blog as well?

And the other way around: if an admin of one of the subdomains has a blogpost that I like can I place this on the main blog?

And the super-admin can he edit any of the blogs on the subdomains?

Just to be sure: every subdomain has the same theme, right? And they can link to their own autoresponder?

Thank you,

Alex