This post will help you how to downgrade your sugar instance. This has some additional steps which is not provided in the SugarCRM instructions.
You should have the original instance and database dump in your server, then proceed to the following steps below:
1. First of all, create the database that the downgraded version will use. Then dump the original database to this new database.
2. Download the SugarCRM installer depending on the version and edition you want. The edition of the original instance and the one you will download should be the same.
3. Create a new installation of the SugarCRM installer you downloaded.
NOTE: Do not use the database we created in No. 1 yet.
4. After installing, copy the ./custom folder and the ./upload folder from the original instance and replace those folders in the new installed edition.
NOTE: Customers below version 6.4.0 should copy the ./custom/ and ./cache/ directories.
5. If there custom modules deployed in the original instance, locate and copy the folders of the custom modules in ./modules folder and paste it in ./modules folder of the new installed edition.
6. Copy the config.php and config_override.php in the root folder of the original instance and replace those files in the new installed edition
7. Update the database settings in config.php file with the correct details. You will now use the database you create in No. 1. Update the db_name with the name of the database you created.
When you load the new instance in your browser, it will show an error. This is because the version of the instance is not the same with the version of the database you created in No. 1, to fix this…
8. Go to config.php and look for the keyword sugar_version. Then go to mysql, use the database we created in No. 1, and type the query below:
select * from config where name='sugar_version'
This is the version of the database. The value of the record should be the same with the sugar_version in the config.php so you must update the sugar_version in the database.
9. If the new instance is now loading, go to Admin > Repair > Quick Repair and Rebuild
That’s it. You’ve already downgraded your sugar instance.