Why was Frederick I only called "King of Denmark" while Christian III was named "King of Denmark and Norway"?
Frederick I of Denmark Frederick I (7 October 1471 – 10 April 1533) was the King of Denmark and Norway. His name is also spelled "Friedrich" in German, "Frederik" in Danish and Norwegian and "Fredrik" in Swedish. He was the penultimate Roman Catholic monarch to reign over Denmark, when subsequent monarchs embraced Lutheranism after the Protestant Reformation. As King of Norway, Frederick is most remarkable in never having visited the country and was never being crowned King of Norway. Therefore he was styled "King of Denmark, the Vends and the Goths, elected King of Norway".
Competitors for the Crown of Scotland With the death of King Alexander III in 1286, the crown of Scotland passed to his only surviving descendant, his three-year-old granddaughter Margaret. In 1290, the Guardians of Scotland, who had been appointed to govern the realm during the young Queen's minority, drew up the Treaty of Birgham, a marriage contract between Margaret and the five-year-old Edward of Caernarvon, heir apparent to the English throne. The treaty, amongst other points, contained the provision that although the issue of this marriage would inherit the crowns of both England and Scotland, the latter kingdom should be "separate, apart and free in itself without subjection to the English Kingdom". The intent, clearly, was to keep Scotland as an independent entity.