A challenge with multisites…

Here’s a challenge that can’t solve.

Schema:

Main Site (Landing page)
/__ sub child site “A”
/__ sub child site “B”
/__ sub child site …. “n”
/__ sub child site (General)

– One site with multiple sites. (solved)
– Each child site most be in a sub-domain. (solved)
– A “n” number of child sites. (solved)
– Each site will have different content from others, but in some cases ALL sites will share one same post, posted just one time. (working on it, at this moment can’t be)
– ONE “General” sub site will contain exclusive post for each user (user 1 just can see post marked by tags 1,5,7. User 2 can see just posts marked with tag 3, etc). These users can be from a sub child site (“A”, “B”, etc) or had a pay subscription. By login in a sub child site you will have access to the general site. (Can this be possible??)

– Any version of WP is installed at this moment, so this option it’s open.

– The “General” site can be the main site, not a sub child site, if this can solve something.

I think this is not too complex, just a little impossible. All ideas are welcome.

Thanks everyone.