Module development and code questions

I have recently published a new text filter module called Image to Media Filters. It is based mostly on Convert Media Tags to Markup. It provides an upgrade path from the img_assist, acidfree, and image_filter modules to Drupal Media Image references.

Hello,

I'm very new to Drupal, and I need help for a job I have to do on a Drupal 8.
Basically here's my needs : from the ckeditor, I need to be able insert a block with an image with some texts and a button.

It would work in the same way as the normal "Upload image" (a popin with fields), but with additional fields (Text, button text, button href).

In other words, I need to have a template which would generate a html block like this :

Hi everyone.

So I'm building a custom application within Drupal 9.4 that integrates with a third-party system. Part of this developments requires me to process an import of CSV data containing email addresses. I need to check the email addresses are valid before sending them onto the external system.

I have been asked to implement a feature that displays a block of frequently-changing content on each page in our site.  That is, the block will show a list of data pulled from an external source that will change once daily.  I'm trying to figure out how to handle this in a way that a) will be permformant, especially with respect to caching; and b) isn't more complicated than it needs to be.

Hello, I'm a junior developper and I want to create a module on Drupal 9, but i don't know where to start.
I first want to create like an "hello world" module to see how it works, can I have some help ? :)

Thanks,
Mélissandre