Where can I download Heroes WOG 3.5, 3.x?

it's much simpler - you need to follow the installation order:
1) install The Shadow of Death (preferred option), or Platinum Edition, or a previous version of WoG
2) when installing The Shadow of Death, the directory is selected automatically (at least for me), therefore move all contents of the Heroes folder to a folder whose path consists ENTIRELY of Latin letters, for example C:\Games\Heroes III WoG
3) Extract all files from the allion1 archive into the allion1 folder, where a file named wog358f.part01 with the WoG icon and RAR extension files will appear
4) Run wog358f.part01, then confirm the extraction path (by default, this is the WogInstall folder, which will be created in the allion1 folder)
5) After unpacking, a WogInstall folder will appear, which should be moved to the C:\Games\Heroes III WoG folder
6) run the install file from the WogInstall folder - after some time, a language selection menu will appear, followed by a window with the inscription welcome - click the next button
a window with list of found components and 3 buttons change patch install and cancel will appear
7) Click change patch, in the opened window specify the path to the Heroes folder (C:\Games\Heroes III WoG) and press ok
8) After pressing the ok key, the list of found components window appears again - click install
after the WoG installation procedure, you will need to install the Russian localization; for this:
1) unpack 3 files with the wog extension from the rubeta358f archive
2) move these files to the directory C:\Games\Heroes III WoG\update
3) run the H3Wupd.exe file in the C:\Games\Heroes III WoG folder
then everything is as when installing WoG

I'll add my two cents.
If there is a failure during installation in a folder with Cyrillic letters, I would recommend the following when specifying the WoG installation path:

1) do not use spaces in the folder name:
instead of
C:\Games\Heroes III WoG
specify
C:\Games\h3wog

2) do not use long folder names, more than 8 characters, i.e., for example,
instead of
C:\Games\HeroesIIIWoG or C:\Program Files\Heroes III WoG
again, it is preferable to use
C:\Games\h3wog