The IEC61850 Driver has been released for 8.1.25, Is it backward compatible and will this be available for previous 8.x releases.
No, no
Upgrades within a version series (8.1.x to 8.1.x) are free, fwiw.
Hi Kevin
Awesome speedy response 
Backward compatibility - No
Availability for previous 8.1.x release - No
So if we are looking to have IEC61850 support the way forward is to upgrade the Ignition version (8.1.x -> 8.1.25)
Yes, you'll have to upgrade to 8.1.25 (or a future version, if you decide to wait) to have IEC 61850 support. No other way.
Thanks Kevin.