Re: error while importing database
You can not restore because the "testing_database" already has Tiki 13.1 data. And you can not just truncate the Tiki 13.1 tables and reload from the Tiki 12.3 version of the database because there have probably been changes made to some of the tables.
To do the upgrade, you should delete the entire 13.1 database, then make a complete copy of the 12.3 version of the database as your Tiki 13.1 "testing_database". (Or backup the Tiki 12.3 version and restore it as the "testing_database"). Then run the Tiki 13.1 install and select to update the database, and Tiki will make the required changes to your "testing_database" tables.
Tom