Answer 1

For some reason the drag and drop API of HTML is very very unintuitive and messed up in my opinion and I had many problems when I created a drag and drop list. For now I recommend you to learn JavaScript first before you come back because it's basically all about JavaScript, I don't know why it's even in the HTML course.

Answer 2

And btw. the drag and drop API isn't even supported by most mobile browsers, so I believe no one uses it nowadays. Most developers probably use some workaround, library or framework instead