I need to install the full OSGeo4W64 version for 2.18.6, Windows 10, 64-bit. However, the previous release page only has the standalone QGIS installer:
Where do I find the full OSGeoW64 installer for 2.18.6?
After following the answer from @mgri below, I get the following error when I try to run 2.18.6:
However, qgis_app.dll does exist, in the correct path.
I have reinstalled twice, each time using the latest full OSGeoW64 installer (which is the only installer I am aware of, and installs 2.18.7 by default). The first time I followed mgri's instructions at the initial install, requesting 2.18.6. The error ensued. The second time I installed 2.18.7, then went back and did a custom install, again following mgri's instructions, and modified the install to revert to 2.18.6. Again, the error.
I am still unable to install 2.18.6, looking for assistance.