render_back_2_1.zip is a legacy add-on will work up until blender version 4.0 render_back_blender4_2_beta-2.1.2.zip is the beta release for the latest release blender 4.2 which should work if your system requirements can handle the latest build of blender which came with a lot of bugs for many people. Because of this, the next update will be released once a stable version of blender is released or if a bug is reported for this add-on.

None, the add-on uses the Windows command line system, therefore it will not work on any other operating systems.