Short answers, pulled from the story.
The Continuation War began on the 22nd of June 1941 when Finnish forces launched Operation Kilpapurjehdus and deployed troops into the demilitarized Åland Islands. This operation coordinated with a German invasion after Soviet air attacks on the 25th of June provided justification for Finland to approve a defensive war.
Field Marshal C. G. E. Mannerheim assumed command of the Finnish Defence Forces on the 30th of November 1939 and led the nation throughout the conflict. He personally refused Adolf Hitler's request to assault Leningrad during their meeting at Immola Airfield on the 4th of June 1942.
The Continuation War ended when the Finnish Parliament accepted Moscow's terms in a secret meeting on the 2nd of September 1944. The agreement required Finland to return to borders from the 1940 Moscow Peace Treaty, cede Petsamo municipality, lease Porkkala Peninsula to Soviets, and pay $300 million in war reparations.
The Battle of Tali-Ihantala began by the 25th of June 1944 when the Red Army reached the Viipuri-Kuparsaari-Taipale line after penetrating the Vammelsuu-Taipale line. This engagement is described as the largest battle in Nordic military history where Finland lacked modern anti-tank weaponry to stop Soviet heavy armor like KV-1 or IS-2 tanks.
Germany supported Finland through secret weapon sales permitted under an agreement signed on the 12th of September 1940 and later by sending additional infantry divisions and assault gun brigades. German Foreign Minister Joachim von Ribbentrop offered hand-held Panzerfaust weapons in exchange for a guarantee that Finland would not seek separate peace which President Risto Ryti gave on the 26th of June 1944.