I've continued conversation with support. Firstly they've sayed that that update is unapplicable to my russian Gratia, and i should go to the service center if i have any wifi issue. After some explanations (about unavailable update to non-russian but still european phones) they've promised to report to their engineers, and still recommended to contact service center. I don't know what to think about it. The situation looks pretty stupid for now. They have that update and i even know it filename (whoa!) but they don't want me to get that file for some reason.
I can only try to install stock rom to my Gratia and try to get FOTA update, if it's present as FOTA. But i don't think that it'll be successfull. BTW i can loose S-OFF in that case.