Questions about accounts in Drupal 7

So, I have a website on Drupal 7 that revolves around two types of accounts - companies and users.

The questions are as follows:

1. If I understand correctly, I need to create two roles - for companies and for users. However, I can't figure out how to assign the appropriate role to a user upon registration, for example, based on their selection in a List (text)?
2. I also couldn't find out how to assign a profile created in profile2 to a specific role?
3. On the company pages, I should have the ability to add users as employees of that specific company. What is the best way to implement this? Should I create a hidden field in user accounts, somehow send an invitation, and fill this field if it is accepted? If so, I can't figure out how to create such an invitation... and how to create such a field?
4. With such a list of employees, is there a way to display access rights settings from user pages (not from the admin panel), so that employees can edit materials on company pages or create materials on behalf of the company?
5. What should I use to give users privacy settings for the fields displayed on their pages? For example - visible to everyone, only to employees, only to themselves.
6. To implement an analog of a "wall" like in social networks, is it better to use a blog module, or simply create a separate content type for these messages?