Looking for link-os 4 changelog and guidance on compatibility

I downloaded the link-os 4 sdk (v1.4.957) yesterday.  I couldn't find a change log in the folder that the installer installed.  Can you direct me to the change log, please?


Also trying to figure out how to navigate compatibility issues.  More specifically, which firmware versions of the iMZ220 are compatible with which versions of link-os 3 and 4?  Can you please provide some guidance? 


Here is why it's important to me.  Our operations group configures the printers before sending them to different parts of the country to our clients.  Meanwhile I develop the iOS app and have the ability to upgrade the link-os SDK within the app.  For example, I want to make sure that:

1.  If I upgrade to link-os 4 inside our app that it doesn't break our printing for printers that are currently deployed and that we wouldn't normally touch.

2.  Also want to make sure that any new printers we configure in house are configured with the optimal firmware version.

3.  We may have some time where our operations people could be deploying printers to our clients with the latest firmware version, before a new version of our app goes out with a later version of link-os.


Thanks for your assistance!