Short answers, pulled from the story.
About 15% of the Russian population disapproved of Putin at the beginning of 2023, according to the Levada Center, a Russian NGO. This figure does not capture the broader anti-war sentiment; Levada polls from 2022 indicated at least 30 million pro-European Russians opposed the invasion of Ukraine.
Alexei Navalny died on the 16th of February 2024 in a prison colony in the Arctic Circle, aged 47. Russian authorities claimed he died of "sudden death syndrome," but his wife and independent analysts rejected this explanation, and authorities refused to return his body to his family for over a week, which his wife said was to allow traces of Novichok poisoning to disappear.
The Bolotnaya Square case arose after police dispersed a "March of Millions" on the 6th of May 2012 as it approached the square. Seventeen people were charged with committing violence against police officers and twelve were jailed. A large number of human rights defenders declared the detainees innocent and held the police responsible for the clashes.
Boris Nadezhdin declared his candidacy opposing Putin and the war in Ukraine and gathered surprise levels of support, with thousands queuing in snow to sign their names in support. On the 8th of February 2024, he was barred from running after the Central Election Commission claimed only 95,587 of his signatures were valid, just short of the 100,000 required, despite his team providing evidence that the claimed errors were minor typographical mistakes.
Strategy-31 was a series of civic protests in support of the right to peaceful assembly guaranteed by Article 31 of the Russian Constitution. Beginning on the 31st of July 2009, protests were held on Triumfalnaya Square in Moscow on the 31st of every month that had 31 days. Writer Eduard Limonov and human rights activist Lyudmila Alexeyeva led the campaign.
On the 4th of March 2022, Putin signed a law imposing prison sentences of up to 15 years for spreading "fake news" about military operations. At least 14,906 people were detained between the 24th of February and the 13th of March 2022, including what OVD-Info called the largest single-day mass arrests in post-Soviet Russian history on the 6th of March. According to Amnesty International, as of June 2023, up to 20,000 Russian citizens had faced heavy reprisals for opposing the war.