Post sorted for users and user registration

Hi,

I’m creating a website with the following 2 challenges. Has someone experience with this?

1. I need to show blog posts based on a custom field related to the user. So I will have like 30.000 users divided in 9 groups. Each group needs to have a custom name. When a user logs in, I need to show on top first his related posts made by administrator. So if I have 9 new blog posts, it needs to show up first the newest post related for him and then the 8 other posts.
At the same time I want to achieve the samen with 2 banners on the page. I want to show up 2 banners, but only visible if the users corresponds to the banner category. If no, I want to show a general banner.
How can I achieve this? A plugin? Which one?

2. I have a list with users. They all have an unique ID. I want to upload them on the backend. I will then send out an email to those users. So they can registrate. But I will need to compare if they registrate that they have a valid ID. If so, they can fill in all other fields and choose their own password. If they don’t have an ID, they can fill in everything , but the admin needs the validate their account! What do I need or who can help me?

Thanks for your answers!

Best regards,
Jochen