Short answers, pulled from the story.
Roskomnadzor manages Russia's national telephone numbering plan alongside the Ministry of Digital Development, Communications and Mass Media. These two bodies oversee a closed system where every subscriber number contains exactly ten digits.
The International Telecommunication Union originally assigned country code 7 to the Soviet Union before its dissolution in 1991. Only Russia and Kazakhstan retained the original digit seven for their systems after most nations switched to new individual codes between 1993 and 1998.
The old code 095 expired on the 31st of January 2006 along with nineteen other Russian area codes starting with zero. A new range of codes beginning with four started on the 1st of December 2005 to replace older zero-prefixed numbers.
Crimea and Sevastopol joined the Russian numbering plan following annexation events in 2014. New area codes replaced former Ukrainian identifiers like 65 for Crimea or 62 for Donetsk People's Republic to allow direct dialing from Moscow to Simferopol using code 365.
Abkhazian numbers switched from Georgian codes to Russian zone 7 starting the 1st of January 2010. This change followed a Memorandum of Cooperation signed between Russia and Abkhazia on the 28th of September 2009.