Shamim's Plugins

1. User can send to how many users same message at a time?
2. Can you please give me screenshot of “Recipient” and “Security” tab of the settings page of this plugin?
3. Give me a screenshot of the page from where user send a message.

Thank you for your suggestion. Currently if you want to change this setup then you will need to add code in functions.php
May be in future version i will add a settings for this.

You can send them a message when they register. You can include any content there. See https://www.shamimsplugins.com/docs/front-end-pm/customization/send-welcome-message-user-register/

I see it is set to V3, Can you activate V2 and use google keys for that version and check if working?

If you want to show new announcements to a certain role of users, then select that role only when create announcement.
If you want to show only a specific user, then send them a message.

I do not know how (or what meta) you used to store that value, So i cannot give you full code.
You can use following code in your theme’s (child theme’s if you are using) functions.php (change necessary code to get that link from user profile)

add_filter( 'fep_eb_email_legends', function( $legends, $mgs, $user_email ){
    $link = '';
    if( $user_email && ($user = get_user_by( 'email', $user_email ) ) ){
        $link = 'Here get that link from $user profile';
    }
    $legends['one_click_login'] = array(
        'description' => __('One click Login link', 'front-end-pm'),
        'where' => array( 'newmessage', 'reply' ), //where this tag will be used
        'replace_with' => $link
    );
    return $legends;
}, 10, 3);

Please follow https://www.shamimsplugins.com/docs/front-end-pm/customization/remove-settings-menu-button/