Understanding the purpose of the "required reviewers" feature

Hi,

I am new to Azure DevOps, and I have a question about the "required reviewers" feature.

As I understand it, one can specify a group to be required reviewers of a repo, i.e. only they can approve PRs into a given branch of the repo, e.g. main.

As a separate setting, one can set the number of required reviewers that need to approve the PR in order for it to be merged.

Say that I specify a team of 5 people as required reviewers, and require only 1 approval to merge a PR. What exactly happens on submission of a PR?

1. Do all 5 reviewers get a notification? Or can the submitter select a particular reviewer for their PR?
2. What if only these 5 people are actively working on the given repo, do then all 5 developers get notified upon any PR submitted by any developer in the group?
3. Is anyone else outside of the group of required reviewers able to approve the PR? (I guess not, but asking just to be sure I understand).
4. Say that a given repo (among many others in the same ADO project) is supposed to be maintained by a given development team of 5 people (among many others in the same ADO project), then in your view, is the "required reviewers" feature the correct feature to use in order to "protect" this repo from changes by other developers than these 5?

Thankful for answers,

Andreas