Impossible to create content or edit image styles after Backup/Restore
How To Update Drupal Core

Follow these instructions:


Make a backup of your Drupal instance (database).
Download the latest release of your current Drupal version.
Extract the [tar ball or zip] Drupal package.
Set your site on maintenance mode 
Delete all the files &amp; folders inside your original Drupal instance
except for /sites and its sub-folders. This assumes that all of your
custom work - including themes - is in the recommended spot - the
/sites folder tree. If you have made custom changes elsewhere you
will need to either preserve them or plan to replace them later.
Copy all the folders and files except /sites from inside the
extracted Drupal package [tar ball or zip package] into your
original Drupal instance location.
Some updates do not include changes to setting.php and some do. See
There is a way - Comment below for more on this. If the update
release includes changes to settings.php you will need to replace
your old settings.php in .../sites/default/ with the new one, and
then edit the site-specific entries (eg database name, user, and
password) in the setting file.
If you have modified files such as .htaccess or robots.txt re-apply
those changes to the new files.
If you have a favicon.ico file that was deleted replace it too
Login to your site as administrator or as user no 1
Run update.php by navigating to
 http://...yourdrupalsitename/update.php and follow the process to
 update your Drupal instance
Disable maintenance mode