I think it depends on which theme you are using, and whether that theme automatically displays the featured image at the top of the post or not. Do you currently have a situation where you have the same image displaying twice in a row because you’ve got both the featured image and the image at the top of the content?

Thank you for your fatest reply. My theme supports display featured image in the top of the post.

And yes, actually i have the situation you described. But i can disable featured image, because during some years i have used a theme wich eliminated first image when i publish post (and set this as featured image).