Drupal 8.x

In a later development stage we reordered the main menu entries. After rebuilding the cache Drupal 8 set back the menu entries in the old order.

Say I have a used cars site, and have fields: year, maker, model, submodel and accessories, each related to the previous fields.

If something missing. such as the maker Toyota, field model missing corolla, I want a user with a proper permission to add corolla to the field model which is related to the maker Toyota, is this possible?

Can I achieve the above by taxonomy? or any recommendation?

Does anybody know how to programatically add a comment to a node?

I have a really boring problem with mit site:

I can see it only as logged in user, work on it, nearly all seems ok but as anonymous user i get only http 500 server error and no message from the site.

The login page has a broken layout (can only see some menu elements)

But if i go in maintainance status, i can see the maintainance message without problems!

If i reinstalled database from a backup, the site works a while, but after some time the old problem still remains and i dont know what triggered the problem ...

I don't know if I'm the only one struggling with this, but I find that when I'm working in Drupal I don't have to work more than 10-15 minutes before my window organization is a huge mess.

I have looked at a number of articles on this subject, but none seem to work for Drupal 8.

My hosting provider (BlueHost) allows add-on domains to be hosted in subdirectories that contain all of the Drupal software for that domain with nothing else in the subdirectory. For example, /www/add-on-domain-one, /www/add-on-domain-two, etc. The add-on domains work exactly the way I would like.

Becauuse this is a shared hosting account, I have access to .htaccess, but I do not have access to any of the Apache configuration files.