WordPress is the CMS that provides the predefined module plugins and these to make your website building process faster and easiest. You can find some free themes for the WordPress official website. But for the demo data, you need to purchase the theme. After that, you will also get the support and updates for that theme.
And the second option is that you can download the free cracked theme. In which the theme author will not provide you the support and you can’t update your theme.so below are some best websites to download the cracked WordPress theme’s. And download free demo data for WordPress themes