Module development and code questions

I am running a Drupal site since Drupal 4 days.............It got upgraded from Drupal 7 to 8 successfully and now it is running Drupal 10.

Before Drupal 8 I was having a block showing recent comments as table with 1. comment subject, 2. author, 3, node title and 4 date-time as fields. I had put code to change the node title to an alternate title (say title_mf which I have in a different table with additional/alternate data for nodes ... node_alt_data)

Hi all !!!

Hello good!

I need help with a problem that we have detected on the website of one of our clients (escofet.com). 

We have seen that there is spam code injected into static pages, but I can't find how it gets there. It does not appear in the database, nor in any ftp file... 

I have deleted the content of the page template and it continues to appear.

In the home page, for example, the following code appears, which is only visible in the source code:

Hi,

I have created a website for a food bank that generates food vouchers by identified referrers. The food voucher code is exchanged for food parcels by the person referred. All works perfectly well but I need to display statistics about the food parcels on the website.

Hello Everyone,

Hope you all are doing well !!

I am a fresher here to Drupal, and my problem statement is as follows:
There is an existing Drupal code (.info and .module files only in repo), which needs to be promoted to Drupal9 which will contain .info.yml file, I have tried to manipulate existing one, but it throws error saying "Missing 'application'" which is added in my dependencies in .yml file. I am attaching screenshots for reference and looking forward for some dedicated support please to fix this error.

Hello,

I am currently trying to build a simple module that calls a Javascript function to ask for a users location data, (lat and long). Then take those two variables and send it back to a function inside of my moduleservice.php file. What would be the best way of doing this, or is my approach improper?

Thanks