Tax is paid by residents, not citizens. Residency is determined primarily by days spent in the country during a calendar year, and in a dispute by your centre of vital interests.
Armenia and Russia have a double taxation treaty. It does not remove the tax; it allocates the right to levy it and lets you credit tax already paid in the other country.
The practical difficulty is evidence: residency certificates, border crossing records, proof of tax paid. We help assemble the file and work out where and what to declare.