It is an official ROM update via OTA. Trust it, nothing to fear
and please remember to perform a factory reset after each update to avoid weird issues.
I have updated to android 8 trought "Local update" and since that time there is a lot of bug. Can I expect a notification for that new OTA update or do I need update to the russian rom before ?
based on what we've 'received' the last year, my guess is there won't be an update anymore and the best support you can get is from the russians, because 'downgrade and factory reset your device' is about the all you will get from BV.