does the new version have all the features of the 2012 version?
Yes. Nothing to my knowledge has been dropped and a few new things have been added.
… and quite a few “under the bonnet” enhancements have been made; to improve compatibility with technical advances (in O/S & HW).
Release notes can be found HERE.
Hey guys, am I right in assuming that the new Nik Collection 4 will NOTstrong text** work with my old “owned” LightRoom 6.1, even though my PL4 does?
One way to find out is to download the free trial… Be sure to have a backup or the installer of the version you’ve used up to now in order to preserve you “way back”. You can also rename the current installation, the difficult thing might be to not miss the components that are installed in less obvious places.
You can also read the System requirements
the installation procedure recognized my LR 5.7 (64-Bit) → Windows
see also Issues with Nik4 - #8 by Wolfgang
and LR shows …