So I'm interested in installing the 1.3 patch for this game so I can get all those bug fixes. But when I looked at the instructions, it says to only install it to version 1.2. But I have no idea what version this is I got from GOG. Is there any way to check?

Is it okay to install 1.3 directly to the GOG version, or do I need to install another patch first?

I installed the 1.3 Community patch after installing the last official patch (1.2) over the GOG version (1.0) and everything works absolutely fine.

So the GOG version is 1.0?
That's good to know. Honestly surprised that it isn't the latest official version; GOG usually delivers that.
How does one check the version in this game anyway?

Wait, nope, it doesn't work.
When I try to run the official 1.2 patch, it gives me an error saying that Daikatana is not installed on my system.

Just skip that patch then and go straight for the 1.3 one. Should also work.