Is it allowed for Russian citizens to take theoretical knowledge examination? If it is not allowed, how to proceed with persons who have already started the examination but have not yet finished?
Training, testing and checking could be allowed if done for the purpose of later operating a non-Russian aircraft i.e. if the student or candidate is e.g. destined to fly as an employee on an EU airline. If the intention is to fly in Russia or Russian controlled/registered aircraft, then such examinations would be support to the use of banned aircraft or operators and hence prohibited. For private pilots (who presumably would be flying themselves and are Russian citizens) such examinations are not allowed. Furthermore, the examination cannot take place in Russia.