This has come up a few times recently, updating from very old firmware. In the end the users just go for it, update, and I believe had no issues that were reported.
I would first check your diagnostic tool version to make sure it is up to date in case things go sideways. Use endpoint HUB.IP/hub/cloud/updateDiagnosticTool to force it to update (if your old platform has that endpoint, not sure). Looks like current version should be 1.1.131
Take a local backup and save to your PC.
Then you should be safe to go for it.
If you run into issues, I recommend DO NOT jump right to restoring a cloud backup. Restoring a backup DOES NOT roll back the hub platform. Normally for rolling back you just go to the diagnostic tool and use the restore previous button, and select a previously installed platform. In your case, you may also need to soft reset and then restore your LOCAL backup because I think there were some back end database changes since the platform version you have now. You should not need a cloud back up at all but its good to have for an emergency.
You will also want to check and update the zwave radio firmware on the C7 after updating. See there special instructions:
Webcore pistons should be included in any local or cloud backups (in the hub database). For extra precaution there is a way to export all your pistons in one batch as a separate backup for just webcore, but I am not sure how since I do not use Webcore.
There is also a rare chance your hub may appear "reset" after you update if the database does not migrate correctly due to changes made. If that happens just restoring the local backup from BEFORE the update should load everything back into the database and get you back going. The z-wave and zigbee radios would not be touched so devices should keep working once database is loaded.
The local (hub database) backups are not tied to a specific platform version, you can in theory load any backup into any platform version. The version listed with the backup is just FYI, and does not need to match up with the running platform.
