(1) what is all that should be in the body tag ?

Answer 1

Body will contain all visual elements, quotes, images, articles, paragraphs, vidéos, audios, all elements that you would show to your website visitors. More information on Sololearn's HTML course.

Answer 2

Revise the course once again since you have already completed it. One should not have such simple doubts after finishing the course.

The content that is possibly visible to you on a web page must have been wrote inside the body tag.

Answer 3

A link to the html course ;)