I know units/lessons from previous years are available to us, but I can’t figure out how to open them up for my students. Could someone give instructions?
To assign previous units to your students go to the settings for that course → Edit section details → version/unit. Here are some screenshots of that process.
Alternatively you can navigate to the URL for the lesson/level you’re interested in, and give the URL to the students to work on.
That’s helpful. Can I go back-and-forth between versions without losing student work?
Yes - Student work is saved on the student end and these are all individual levels that are not linked. You should be fine!