Publishing & sharing
Sending a class to one version
Hold one group on one version without freezing the experience for everyone else.
An experience has two kinds of link, and they are two addresses rather than a setting to choose between. Both work at the same time.
The plain link
The one in the header. It follows every future publish, so whoever holds it always gets your latest work. This is the right link for nearly everything.
A version's own link
Copy it from version history, from the row of the version you want. It goes on serving that version however many times you publish afterwards — the link for a class sitting an assessment, or a course that has been signed off.
Why not Freeze the experience
Because Freeze is one answer for everybody. Choosing it for one class re-points every link already handed out, including the ones you sent to people who should be seeing your newest version.
Two addresses avoid that entirely: this January's cohort keeps January's content, everyone else moves on, and you do not have to remember which setting the experience is in.
What is frozen, and what is not
Only the content is frozen. A learner on a version link meets the same activities, the same attempt allowances and the same rules as everyone else, and their work counts towards the same single grade — one experience is one grade however many links reach it.
So do not use a version link to give a group different rules. Use it when they must all see the same thing.