Short answers, pulled from the story.
The 2011, 2013 Russian protests began after legislative elections on the 4th of December 2011 sparked immediate controversy over widespread fraud. Polling districts across Russia closed following reports of more than 1,100 official irregularities nationwide within days of the vote.
Alexei Navalny emerged as a central figure by branding Putin's United Russia party as the party of crooks and thieves on his LiveJournal blog. Boris Nemtsov joined the movement as an opposition leader and former deputy prime minister while other speakers included writer Boris Akunin and rapper Noize MC.
Police arrested about 400 protesters on the 6th of May 2012 before Vladimir Putin's inauguration including Alexei Navalny Boris Nemtsov and Sergei Udaltsov. On the 7th of May at least 120 more protesters were arrested in Moscow alone.
On the 23rd of February 2012 a massive pro-Putin march ended at Luzhniki Stadium where police estimated 130,000 attendees. Police reported 138,000 to 150,000 peak attendance for the Anti-Orange protest that occurred on Poklonnaya Hill near World War II memorial complex on the 4th of February 2012.
State TV channels generally ignored protests until the 10th of December when all main state-controlled stations began covering events professionally. Ren TV remained the only federal station mentioning protests extensively before that date while Western media covered protests starting the 5th of December with Fox News initially using footage from Athens riots showing Molotov cocktails before removing the report.