Author access / accidental deletion etc..

Hi i am adding a new user for the first time so that they can do some work on my websites, initially i am setting them up as an auther to learn and work on blogs only until they get to learn how it all works.

I have set up an account for them and all looks good but in the post section they have access to all posts and i fear the potential of accidentally deleting other posts.
also if possible i would like to check their work prior to publishing.

how do i go about this?

A) can i validate / authorise their posts before they go live i.e not allow them to have access to the final publish button?

B) is it possible to lock a post in the dashboard once it is live so it can’t be edited or accidentally deleted without permission?

I look forward to any input / help ??