Module development and code questions

I have tried to include an iframe (For example:- with src="domainA.com/page1") in Domain B for accessing a page of Domain B.

But I got an error that Domain B has been blocked by Domain A due to CORs policy.

I tried to possibilities:-

 1) I have included domain B in the settings.php of Domain A as a trust_host_pattern and hence that error was not showing now.

But still I am not able to access the page, which I tried to access using iframe.

2) I have tried to enable CORs settings in sites/default/services.yml like below:-

Hello,

I'm using Acquia site studio, and I don't have much experience.

Just a tip, if you didn't know: Drupal contributors with 35 or more issue credits gained over the past year can get a free PhpStorm license. See Free PhpStorm license for Drupal contributors.

Hi, in a custom form I have several php files, both in the form and Controller folder.
From these files I need to call some functions that are the same for many. Until now I have rewritten them but to avoid errors, I would like to write them in a single file but I am not clear how to do it

Hello,

I'm having problems controlling access to nodes since I upgraded to Drupal 10. The options I had explored, by taxonomy or by content, have not yet been upgraded to Drupal 10. Any solutions?
Thank you so much.

Hello community, I am new to Drupal and I am investigating how it works, the question is that I deleted by mistake the content article that brings by default, I searched and found how to create a new one, but using it does not publish it on the main page.
Does anyone know why? thank you very much!