Rooted device, modified the hosts file and rebooted but still have access to blocked sites
Just try adding these three hosts name and replace ip address 127.0.0.1  

    facebook.com  
    www.facebook.com  
    m.facebook.com
    mobile.facebook.com


As I checked when typed facebook.com, the site will be redirected to m.facebook.com, so we won't be able to access.