Will all modules be compatible and safe with my site?

Some modules have special requirements such as webserver or operating system, but most modules written for XOOPS 2.0 work on any version of XOOPS higher than 2.0

However, the development of XOOPS means that some modules only work with later versions of XOOPS because these modules use functionality introduced in this XOOPS version.
If you run the latest XOOPS version, you should not experience incompatible modules - at least not due to XOOPS version.

This Q&A was found on XOOPS Web Application System : https://xoops.org/modules/smartfaq/faq.php?faqid=170