Hi Vahe

Thank you for reaching out to us.

1. You can use this hook: wpdatatables_filter_table_description

add_filter( 'wpdatatables_filter_table_description', 'verse_show_entries', 10, 3 );
function verse_show_entries( $object, $table_id, $wpDataTableOBJ ){
    $object->dataTableParams->aLengthMenu = array(
        array(
            10,
            25,
            50,
            75,
            100
        ),
        array(
            10,
            25,
            50,
            75,
            100
        )
    );
    return $object;
}

Add it to the functions.php file of your theme, or child theme, and it will not be affected by the plugin's updates.

2. I'm afraid you can only set sorting for the entire column, not only the displayed data.

3. Unfortunately this cannot be achieved using the plugin's builtin features.

I'll kindly ask you to add it as a feature suggestion on this page. 

Features are pushed up on our "to-do" list when there are a lot of customers requesting those features, so having your vote as a customer can be beneficial to this feature being developed sooner.

It probably can be done with some custom work, but our developers are very busy at the moment, working on some priority tasks and fixing bugs and issues with our plugins, so they won't be having the time for custom work in near future.

But we can recommend these services for customization:

https://codeable.io/?ref=l1TW1

https://wpkraken.io/?tms-plugins

They do develop such solutions, so can you please send your inquiry to them?