I have a similar situation. I have a Flirc Gen 1 with firmware 4.9.3. I am running Windows 10 latest version.
When I downloaded the Flirc software, I apparently got 3.25.4. When I do a check for new version, I tells me that version 3.25.5 is available, but after the download and upgrade, I still have 3.25.4.
In the log file, it says that Gen 1 devices are not supported.
I found the forum article about Gen 1 support. From there I downloaded the 3.25.2 version of the software. I installed it and it complains that it needs firmware 4.1, which seems older than what I have. I cannot say for sure if 3.25.2 works or not. It is good to know that there is no intention of discontinuing support for Gen 1 devices.
Anyway, at this point the most important issue for me is that I want to know what a certain button on my remote actually sends. I there a way to find out? I suppose it is somewhere in the Flirc configuration file, but unfortunately that is not human readable (like f.i. a .xml file).