I think for 1.92 it's best to do manula update:
- Backup your DB
- Backup your upload directory
- Backup your config.php
- Remove whole file for webserver
- Put whole file from 2.0
- Launch install and choose the same DB than old 1.92
- Go to the end of install
- Put your backuped upload directory to the new upload directory.
Assistance on LimeSurvey forum and LimeSurvey core development are on my free time.
I'm not a LimeSurvey GmbH member,
professional service on demand
(or search sondages pro).