I'm an IT technician and some client, with Moodle 3.4 wanted to upgrade to 3.9, but before, he (and me, so I'm not used to Moodle), needs to know if the grades, participation, forum post, etc, will be there after the upgrade. I suppose that all of that goes by the database connected to Moodle, but need to be sure before I answer him.
So, it's the upgrade safe for all that data?
And, It's safe to upgrade directly to 3.9 or should be done upgrading version to version till 3.9?
Other question, Will be safe to upgrade directly to 3.9 or it's better to step in all the mayor versions from 3.4 to 3.9 (3.5, 3.6, 3.7 and 3.8) ?