Short time after publishing of jqGrid 4.7 at Dec 8, 2014 Tony Tomov have changed license agreement (see jqGrid 4.7 published at Dec 16, 2014). Because of that I started so continue to develop my own fork of jqGrid based on jqGrid 4.7 (the last version available under MIT/GPLv2 licenses) under the name free jqGrid. You can download it from github. More information about it is available in readme and in wiki.
So there are exist now Guriddo jqGrid JS which can be purchase here. So the full name of jqGrid 4.8.2 is Guriddo jqGrid JS 4.8.2.
The answer which you referenced shows how to "subclass" internal jqGrid method $.jgrid.from
to have access to new custom "lastSelected" parameter. The technique is tricky, but it works with old versions of jqGrid.
If you would use free jqGrid 4.8 or later then you can just use new lastSelectedData
option, which have the same meaning like "lastSelected" parameter in my old answer. At the end of readme you will find some demos. The first demo is what you need.