Short answers, pulled from the story.
Urho Kekkonen served as president of Finland from 1956 to 1982, a tenure of nearly 26 years, making him the longest-serving Finnish president. He dominated Finnish politics for 31 years in total, including his earlier terms as prime minister.
The Paasikivi-Kekkonen doctrine was Finland's foreign policy of "active neutrality," under which Finland maintained independence while keeping good relations and extensive trade with both NATO members and Warsaw Pact countries. Kekkonen continued the policy established by his predecessor President Juho Kusti Paasikivi. Critics referred to the policy of appeasement as Finlandization.
In October 1961, the Soviet Union sent Finland a diplomatic note proposing military consultations under the Finno-Soviet Treaty, just as a multi-party opposition alliance called Honka-liitto was backing a rival presidential candidate, Olavi Honka. Honka withdrew his candidacy following the note, leaving Kekkonen to win the 1962 election with 199 of 300 electoral college votes. Whether Kekkonen himself organised the Soviet intervention remains debated.
On the 18th of January 1973, the Finnish Parliament extended Kekkonen's term by four years through a special Derogation law, passing it 170 votes to 28. Kekkonen had implied that only he personally could reassure the Soviet Union that Finland's pending free-trade agreement with the EEC would not threaten Soviet interests, which secured the crucial support of the right-wing National Coalition Party for the extension.
Kekkonen went on medical leave on the 10th of September 1981 after falling ill during a fishing trip to Iceland and formally resigned on the 26th of October 1981 due to ill health. It is commonly believed he suffered from vascular dementia, probably caused by atherosclerosis. He died at Tamminiemi on the 31st of August 1986.
The Finnish Constitution was reformed between 1984 and 2003 in direct response to Kekkonen's concentration of presidential power. The reforms introduced a two-term limit on the presidency, restricted the president's role in cabinet formation, replaced the electoral college with direct popular elections, prevented the president from dissolving parliament without the prime minister's support, and strengthened the prime minister's role in foreign relations.