Aleksey wrote:So the question is - do I need add russian support or not?
For Windows updates you don't need to as they're language independent. There are some exception like .NET Framework, Internet Explorer, and some more. If you need to uppdate Windows 7, then you need to add Russian language support because IE11 wouldn't be installed otherwise. Similar applies to .NET Framework and its Russian language pack (the framework itself is language independent but there are language packs).
Do I need use command "wsusoffline\cmd\AddCustomLanguageSupport.cmd rus" to add russian language?
Yes, if you need to add Russian language support.
What about Microsoft Office updates?
Not sure about those. It depends on the MS Office you have. Click2Run Office can't be updated by WSUS Offline at all, the "regular" MS Office has some language dependent files judging by the static files shipped with WSUS Offline (e.g. wsusoffline\static\StaticDownloadLinks-o*-rus.txt).
Regards
Dalai