how to change title in mail for wordpress website from wordpress to customized text?

Todo this just goto page..
/wp-includes/pluggable.php

Search $from_name = 'WordPress'; and  Replace Wordpress word with
$from_name = 'your own name';

How to display total blog posts in a static page?

To display total blog posts in a static page which are created by the developer, need to follow below steps..

1. Create a page with the name posts.php in theme folder which the site using.
2. Copy paste below code

<?php
/**
 * Template Name: Posts Page
 * Description: A Page Template that adds a sidebar to pages
 *
 * @package WordPress
 * @subpackage Twenty_Eleven