Short answers, pulled from the story.
The European Economic Community and the Soviet Union signed their Cooperation Agreement on the 18th of December 1989. This document came into force on the 1st of April 1990 to establish the first legal framework for relations between what would become the EU and Russia.
In 2008, the European Union accounted for 52.3% of all foreign Russian trade. That same year, Russia exported €173.2 billion worth of goods to the EU with energy and fuel supplies making up 68.2% of those exports.
Since 2004, the Russian exclave of Kaliningrad Oblast has been surrounded by land on all sides by EU members after Poland and Lithuania joined the EU and later the Schengen Area. Direct air access became impossible following the 2022 invasion of Ukraine when the EU banned Russian flights from its airspace.
Sergei Skripal and his daughter Yulia were poisoned with Novichok nerve agent in Salisbury on the 4th of March 2018. British Prime Minister Theresa May requested a Russian explanation by the end of that month regarding this incident.
Diplomatic relations between Russia and the European Union broke down completely following the ongoing invasion launched in 2022. The European Parliament passed a motion declaring Russia a state sponsor of terrorism on the 23rd of November 2022.