Module development and code questions

In one view I have chosen an entity reference field as a filter.
The filter works only by typing the node number.
To allow the user to choose the Registry, I modified the field transforming it into an autocomplete text field and wrote a query to filter the data but it doesn't work and I didn't understand why.
The name of the filter field is
field_request_target_id

Hello, like my subject states I was trying to set a field with unlimited number of values down to a limit of 2. I get:

1 error has been found: Limit

There is data for this field in the database. The field settings can no longer be changed.

and

"There are 11 entities with 3 or more values in this field" 

I was able to find two entities that I could remove the extra field items but it still says 11. I've gone through every single one and can't find any with more than 2 items.

This is my attempt to create a compund field with number field. I have created a compound field with fields(two text fields, two link fields) and finally added one number field. 

The problem is that, all the fields are stored properly in the database, but the the number field is not pulled when in re-edit node. But all other fields are pulled. 

The widget code

Hi,

I have spent hours trying to find a way to obtain the values of various fields within a fieldset, but, I have not found anywhere the explanation, to understand it, apply it and then teach others who have encountered the same situation. Could you help me, I'm working with Drupal 9

Thanks

I am using Full Calendar to schedule events for specific User roles (users are applied with different roles). Is there a way to send notification to the users once an event has been scheduled and reminder about the event??  

Scheduler module is something I looked at and it talks more about publishing contents based on timers. Not emails (I may be missing something). Any other module available to help send email to group of users as reminders or notifications? Thanks!

I am building a compound field with (text, url) field, After seeing some of the examples. 

I want to add a number(positive number field min 1 to max upto more than 1000). However I could not get any examples for Drupal 8+. 

Could someone guide how to add number field to fieldWidget and fieldType. 

If possible give any example and the array to create the field inside the compound field. 

Thanks