Module development and code questions

Hello all,
I've been puzzling over some strange behavior for a while now. I have integrated a Drupal page into another page via iFrame. Works fine, CSP-Header & Co are set correctly (as far as I know) only when logging in via modal form (Bootstrap) the user is authenticated correctly according to the log, but the call right after that gives an "access denied" again. (CacheableAccessDeniedHttpException). Without iframe it runs smoothly - and once logged in without iframe it continues authenticated in the iframe. Permission settings are definitely not the problem.

How to write the custom Drush Commands in Drupal 8?

Can someone tell me what the icons and buttons were made with on this site ..

Home | Front Range Fire Rescue (colorado.gov)

I have adapted the embed code to my site...

Home | Town of Dinosaur (colorado.gov)

I would like to know an easier way to do this.  I am only a programmer for the site and don't have access anything except my landing pages.

Thanks..  Jim

I am unable to locate the Drupal 9 API page for dpr(). Here is a link to the
Drupal 8 API for this function.

What is the Drupal 9 replacement for this?

A function with that name exists for Drupal 9, as $nodedump = dpr($nodes, TRUE, 'mymodule'); does not trigger an error.

However, it doesn't work. $nodedump is always empty.

Hi,

Is there a way I can add new nodes and update existing ones (if I have the uuid or nid) from an external process (php/python) that would run on the same server as Drupal.

Is there any API Drupal exposes that can be used for that?

Can I program a module that would be used as such API?

Another option is to store the new and updated nodes' data in a DB and write a module that reads and updates Drupal nodes, but I don't know how to make this module run every N minutes without user interaction? (can it be done with cron?)

* latest Drupal 9.x *

So I got this multi-cardinality field of type `text_long` which always contains 3 entries. Let's call them field_1, field_2 and field_3.

After saving the containing node, all the empty fields are getting stripped from the saved entity when they are empty, this is not what I want.

So whenever someone saves a value into one of the latter fields (let's say field_3) because the field_1 and field_2 are empty, the first 2 will not be saved and on subsequent node edits the values I put into field_3 are being shown in field_1.

What I've tried so far: