Not officially supported. If you absolutely need older version (v2.5.1), PM me. You’ll need a JTAG flasher.
Clarion PX4226AA Firmware Update: The Ultimate Guide to Features and Performance clarion px4226aa firmware update hot
This article provides a comprehensive guide to understanding, downloading, and installing the necessary updates to improve your performance. ⚠️ Important Note: Firmware Disclaimer Not officially supported