If you want to upload the featured image and not show it in the single post, you can disable it with the Page Header add-on in “Customize > Layout > Page Header”.
I upgraded WordPress to 4.7, what I found is that after I enabled featured image, there are two same images appear with the title in between as I put the image under the title. The image on top of the title cannot be hidden even I set ‘Customize > Layout > Page Header > Single Post Header Position’ to hide. How to fix this?