Short answers, pulled from the story.
Vladimir Putin made new proposals during his annual address to the Federal Assembly on the 15th of January 2020. This marked a sharp turn from earlier positions he had taken in March 2018 when he explicitly stated he was not going to change the Constitution.
The clause regarding maximum presidential terms removed the phrase in a row to nullify previous terms served by Vladimir Putin. A presidential candidate must live in Russia for at least 25 years and may never have held foreign citizenship under these new rules.
Legislative assemblies of all 85 federal subjects had approved the amendments by the 13th of March. Ratification by two-thirds of the 85 regional legislatures was needed for an amendment to come into effect which meant 57 regional ratifications were required.
The amendments were rescheduled for the 1st of July 2020 with early voting allowed from the 25th of June 2020. With 98% of the ballot counted, 78% voted in favor versus 22% against during this nationwide procedure.
The commission concluded that the amendments disproportionately strengthened the position of the President on the 23rd of March 2021. They identified serious flaws in the adoption procedure and noted that changes to judicial provisions affected core elements of judicial independence.