The version of Highway Blossoms and Highway Blossoms - Next Exit, I have bought on GOG are both version 2.5.4.
The highest patch number here is 1.2
Will this patch work with the GOG 2.5.4 version?
Viewing post in Highway Blossoms - R18 Patch comments
The correct patch to use for your version should be 1.1.1.
Apologies for the confusion — the version number listed on GOG did not come from us.
The 1.2 patch is for the upcoming 1.2 update that will be pushed to digital storefronts soon (which will also correct the version number listed on GOG, as we now have direct access to it).
(※ Version 1.2 is what shipped on our physical releases, hence why the patch is already uploaded here.)