Module development and code questions

I would like to add a menu link to one of the menus, preferably the User Account menu.  However, it should function like an Admin Menu, so for the sake of simplicity, let's say I want to add a Menu Item to "Edit the Current Page".

It was attempted here, but the details are sparse, and it did not work for me, even with the suggestions about cacheing at the bottom.  It retains the Node ID whenever the block was first made after a Clear-Cache.  The Node ID doesn't refresh.

I am building a custom module which has a form which functions as a calculator for a specific use case. This form contains a table which collects user input in rows, allowing the user to add new rows as needed.

My problem is that I need a callback function that accesses each row, performs calculations on the values in that row and return results for each row. I don't know how to access each value as the field name is the same on every row. I have tried using $key to give each field a unique name, but that does not help me loop though 'x' number of rows the way I need to.

How to create custom module for banner, i have content type banner with img field that is link to another page, are somewhere any examples for this?

I have created a compound field with 2 subfields (title, body). Now I need to add another subfield (Footer) to the same compound field.

Though I have added the new field definition in all required places (propertyDefinition,schema,formElement), field is not getting created in the table. How to achieve this? Kindly help me on this.

I've tried aggregation, it works and it's comfortable. I have a greater and more complex need.
In the views I have 2 content types. Each with a numeric field.
The aggregation should display the total by content type and then calculate the difference between the 2 amounts.

I would like to make it programmatically. Can you route me to suggesting what to read?