Module development and code questions

I have a content type called "Resources" and this has 2 taxonomy terms "Main folder" and "Subfolder". When I create content for the Resources content type, I choose a main folder and subfolder combination. I have a view created based on this content type and the view has "Main folder" and "Subfolder" fields exposed for filtering. 

When I select the main folder option, I want to populate the subfolder with the corresponding options from the backend. For example, if my data on the backend is as below:

Hallo I am trying to write url rewrites as in D7 hook_url_inbound_alter, here is my module

services:
  lg_url_rewrite.path_processor_lg_url_rewrite:
    class: Drupal\lg_url_rewrite\PathProcessor\URLrewrite
    autowire: true
    tags:
      - { name: path_processor_inbound }

Hello everybody! :) I'm getting straight to the point.

So, my goal is to extend menu links so that they can not only have other (manually created) menu links as children but also (upon frontend rendering) have an additional list of automatically created child links. As an example, a menu link could have an additional reference field to a taxonomy term and then all taxonomy terms beneath that term would get rendered as menu link children in the frontend, possibly even nested.

In the user profile page, I have 2 taxonomy terms - class and group. When creating every user, a class and group will be selected. So the user details will be like : "User A, class - Respondents,group - Generic". There is a message board tied to default comment. So when the users comment on the messag eboard, it should mention: "Submitted by User A, Respondents, Generic". Right now, "Submitted by" shows only the user name. Is there a way to attach the 2 associated fields to this? 

Is there a way to manipulate the data from Workflows, the archive, draft, published states? Any suggestions on the best way to save 700 nodes from one content type to switch them all from Draft to Published?

Hi

I have a view, some exposed filters ajax enabled. When I select a filter the view updates through Ajax.

Im struggling to see how this happens?

I'm gussing there is a JS call somewhere can I just call this same js function?

I can build a module where I create my own buttons, but I cant find any information on what I need to call to create the ajax update.

If I disable JS I get a url like ?myfilter=value. Do I just pass this through some JS function?

Thanks for any help on how to get started