Updating CiviCRM Module in Drupal 7
Check what settings you have for CIVICRM_MEMCACHE_PREFIX in your civicrm.settings.php file. You can't define a constant more than once.  Maybe copy/paste the relevant sections into your question.  Don't include the whole file.
The 'Deprecated function' relates to the Drupal backup_migrate module - nothing to to do with CiviCRM.  Have you just changed php version?  That message relates to a changes introduced in php 7  Make sure your Drupal modules are updated.