Short answers, pulled from the story.
Russia Day commemorates the adoption of the Declaration of State Sovereignty of the Russian Soviet Federative Socialist Republic on the 12th of June 1990. The declaration was passed by the First Congress of People's Deputies and marked the beginning of constitutional reform in the Soviet state. It did not declare outright independence; full independence came later in 1991.
The Supreme Soviet of Russia proclaimed the 12th of June a national holiday in 1992. A presidential decree on the 2nd of June 1994 reaffirmed it as a national holiday, and a further decree on the 16th of June 1998 gave it the official name "Russia Day." The 2002 Labour Code then placed that name into statute.
Before 2002 the holiday was officially called the Day of Adoption of the Declaration of State Sovereignty of the RSFSR. The shorter name "Russia Day" was formally established by a presidential decree in 1998 and confirmed by the new Labour Code in 2002.
A Levada Center survey from May 2003 found that 65 percent of respondents called the holiday the Independence Day of Russia. However, that name has never appeared in any official government document. Many Russians also view the day simply as a day off, and for some it carries difficult associations with the economic hardship that followed the Soviet dissolution.
Concerts and fireworks take place in cities across the country, and the President of Russia presents State Awards to prominent writers, scientists, and humanitarian workers. Notable past celebrations include a historical military parade at Red Square on the 12th of June 2004, an air show in 2003 featuring the Russian Knights and Swifts aerobatic teams, and in 2008 a three-day celebration that included events in Tomsk, Samara, and Moscow.
In 2019, the self-proclaimed Donetsk People's Republic declared Russia Day a state holiday within its territory.