Short answers, pulled from the story.
The primary law governing Russian citizenship is federal law 138-FZ, which entered into force on the 26th of October 2023. It replaced the previous law 62-FZ, which had been in force since the 1st of July 2002.
Foreign nationals may become Russian citizens by admission after residing in Russia for more than five years with a residence permit, demonstrating proficiency in the Russian language, and proving a legal source of income. The residence requirement is reduced to one year for asylum seekers, refugees, and those with extraordinary scientific, technological, or cultural contributions, and may be waived for citizens of other post-Soviet states who have served at least three years in the Russian Armed Forces.
Former Soviet citizens permanently resident in Russia on the 6th of February 1992 automatically became Russian citizens unless they applied to refuse citizenship by the 6th of February 1993. Other former Soviet citizens could obtain Russian citizenship by registration if they migrated to Russia between the 6th of February 1992 and the 31st of December 2000.
Russia's approach to dual citizenship has shifted repeatedly. The 1978 Soviet law formally barred it; the 1991 post-Soviet law permitted it only with bilateral treaty partners. Dual citizenship was actively discouraged by Russian agencies until after 2014, when rules began relaxing for citizens of certain post-Soviet states. The requirement to renounce foreign citizenship before naturalizing as Russian was completely abolished in 2020.
Russia signed dual citizenship treaties with Turkmenistan in 1993 and Tajikistan in 1996. Simplified naturalization agreements were signed with Kyrgyzstan and Kazakhstan in 1996, and a multilateral agreement added Belarus and Kyrgyzstan in 1999. The five-year residence requirement for naturalization was later removed for citizens of Belarus, Kazakhstan, Moldova, and Ukraine.
Following the 2022 Russian invasion of Ukraine, expedited acquisition of Russian citizenship was extended to residents of Zaporizhzhia Oblast and Kherson Oblast in May 2022, and then to all of Ukraine in July 2022. Ukrainian citizens had already been exempt from proving renunciation of Ukrainian citizenship since 2017, and residents of Donetsk Oblast and Luhansk Oblast had been eligible for expedited citizenship since 2019.