Drupal 8.x

How can I properly set a class for body tag for the front page?
mytheme_preprocess_html() have an access to body attributes, but it doesn't know if the page is front.
And mytheme_preprocess_page() have is_front, but I can't set attributes in there.

In Drupal 8 will auto-updates to Drupal core be added in the near future?

So I developed a few web sites between 2008 - 2010 with Drupal. I think it was Drupal 6. Though I don't remember for sure. I am not a coder nor programmer. But I found Drupal very scalable and easy to work with especially once you add the right modules.

Now my question is in regards to Drupal 8, and more importantly Drupal 8 vs. Wordpress.

I have not needed to develop any web sites since 2010. So I have been out of the game, as it were. I don't know really what has changed with Drupal.

Who can help and guide me from stage to stage, the drupal? because I was new. Thank you

I am trying to get an advance feel for D8 and have a local installation from Bitnami. I want to have a drop down submenu from the main menu in my very simple site but can't see how to get one to work using the supplied Bartik theme.

I guessed it might be a theme issue but there don't seem to be many other freely available D8 themes yet to try instead, at least the ones I have found don't work either. I have also installed TB megamenu but that doesn't seem to do it either.

https://www.drupal.org/node/1903374 gives instructions for disabling the render cache in Drupal. Since I'm just playing in a sandbox where I'll be experimenting with themimg, this is want I want to do.
The instructions are as follows