Short answers, pulled from the story.
Dmitry Medvedev proposed extending presidential terms from four years to six years and parliamentary terms from four to five years. This proposal marked the start of the most substantial constitutional amendments since 1993.
The State Duma voted during three readings between the 14th of November and the 21st of November 2008. The final reading occurred on the 21st of November with 392 members voting yes while 57 opposed it.
All 83 federal subjects had approved the amendments by the 18th of December 2008. Article 136 of the Constitution required approval from at least two-thirds of these federal subjects before the changes could become law.
United Russia, the Liberal Democratic Party, and Fair Russia all supported the legislation throughout all three readings. Only the Communist Party represented by 57 parliamentarians rejected the bill during every vote.
President Medvedev signed the finalized text into law on the 30th of December 2008. Rossiyskaya Gazeta published the official document later that day and the amendments officially came into force on the 31st of December 2008.