I can add this to the list of requested updates. In the meantime, you could do it with a custom child theme. More info here...

https://wpreviewslider.userecho.com/knowledge-bases/2/articles/553-use-child-theme-to-customize-the-review-template-more

There is a way to do it, but it will require a plugin update for me to add that feature. I can also tell you which file to edit if you would like to modify the plugin yourself. I'm probably about a week away from an update.

I'm not exactly sure what you are asking, but you can create a review submission form to collect reviews. You can include links to other review sites so they can go leave a review there if they want. However, the plugin can not submit a review to Google for the customer. Google or any of the other sites require the customer leave the review on their site.

I would need to log in to your site to investigate. You can send temp admin credentials to landjllc@gmail.com if you want me to take a look.

It checks the name and timestamp of the current reviews in the database and compares them with the import. If a duplicate is found it skips it. So, they add unless already in there. They do not overwrite.