The validity period of an electronic visa and the permitted length of stay can only be extended in exceptional situations, such as being unable to leave Russian territory due to urgent medical care, unforeseen compelling circumstances, or natural disasters.
Extensions of the unified e-visa and the allowed stay are managed by the Ministry of Internal Affairs of the Russian Federation or its regional branches, based on where the migrant is registered. If no migrant registration exists, the extension is processed at the location of the actual stay by issuing a standard (non-electronic) visa.
If you already hold a valid Russian visa in your passport, there is no need to apply for a unified e-visa. You may enter the Russian Federation using the existing regular visa throughout its validity period, free from the limitations associated with the unified e-visa. Moreover, acquiring a unified e-visa does not extend the validity of an existing regular visa.