Updated Alt Text in HTML from Media Library

Hi,

I’m having trouble finding the direct answer to this in the documentation, so I’ll try here. Two questions:

1. I would like to update all the alt text in all of my Posts (the HTML in the body) with the alt text found in the Media Library. Does this plugin facilitate that? It looks like you can do this in the Bulk Updater by setting the field “Image Alt Text Settings” to “Update in Post HTML” and setting the Image Alt Text Settings to %imagealttext%. Is that right?
2. Does the above work on all images/posts, or only on posts where the image is attached to the post? (Another way of asking might be, Does the plugin cycle through all posts or all images?)

I am not a Pro user but will likely become one if this solves my problem.

Thanks!