I noticed in ThemeForest many themes that implement the ability to insert reviews inside the post. The problem of these templates is that if I have a site that has 1200 review and I want to change the template, how do I import all the reviews in the new one? I should change over 1200 individually review?
You Mean comments on a post?
If you just change theme they should remain on the posts otherwise you can export the posts and comments via XML or similar and import them into the new theme.