The current versions of our extensions work with Joomla 3.4.8 to 3.8. As part of our preparation for Joomla 4, we have dropped support for older versions of Joomla 3 in almost all of our extensions. Older versions of our paid extensions are available on request.
We no longer provide extensions for Joomla 2.5 except for Eyesite, which will remain available for Joomla 2.5 until the end of 2017.
We strongly recommend that you keep your site up to date with the latest version of Joomla. From time to time significant security issues emerge, and sites that are not updated are quickly attacked once details of the problem are published. In general you can assume that our extensions work on new minor releases of Joomla, but if your site is critical to your business you should have a parallel test site where you can test upgrades before implementing them in your live site.
We will always offer our best advice, but if you want us to research a complex or time-consuming problem, it must be on the latest version of Joomla with the latest version of our product.
There's a table of Joomla versions and support dates at http://docs.joomla.org/Joomla!_CMS_versions
Our extensions work with PHP 5.3 to 5.6, and PHP 7. If you have not yet upgraded to PHP 7 you should make plans to do so. Sites run noticeably faster with PHP 7, and Joomla 4 requires PHP 7 as a minimum.