Revert back to the previous dev version of a module using composer
You have to refer to the dev branch and reference the SHA of the version of dev you want in Composer.

Example:

composer require drupal/field_group:3.x-dev#COMMITSHA

This will fetch the dev branch of version 8.x-3.x at this specific commit. To get that commit itself, you’ll have to find it on the git page for the project ( which now goes to GitLab).

I can’t find the exact one you are looking for (I’m on mobile) but here is an example.

https://git.drupalcode.org/project/field_group/commit/a4bd38698187c30184d5c76fd884be86e2091fe7

So you’d do:

composer require drupal/field_group:3.x-dev#a4bd3869