Hello, 

What is the best practice to update the hardware controller to a newer version without losing data/settings?

Situation today: 

OC300 V1    1.12.1 Build 20220803 Release 39765

The controller is installed in the headquarter, 48 small sites are connected by MPLS

I need to do an update to the newest version if possible.

Can I perform the upgrade from 1.12.1 to 1.25  or is it better to perform updates to all the different versions between 1.12 and 1.25? 
What kind of backup do i need to make before starting?

Best regards

Stijn