Can I restore a pfSense configuration to a different version?

From PFSenseDocs

The pfSense configuration file from 1.2.x versions can be restored to any 1.2.x version, including going from newer releases to older ones and vice versa. 1.2.x configurations can also be restored to 2.0 systems, and they will be converted to the format used by 2.0.

You cannot restore a 2.0 configuration onto 1.2.x or earlier releases.

Configurations are pfSense version specific. The version of FreeBSD used is not relevant.