Short answers, pulled from the story.
Constitutional monarchy, also known as limited or parliamentary monarchy, is a form of government where the monarch exercises authority according to a constitution rather than making decisions alone. This system binds the monarch by an established legal framework that prescribes limits on powers and authorities.
Poland developed the first constitution for a monarchy in continental Europe with the adoption of the Constitution of the 3rd of May 1791. This document became the second single-document constitution in the world following the United States Constitution.
Queen Anne became the last monarch to veto an Act of Parliament on the 11th of March 1708 when she blocked the Scottish Militia Bill. Hanoverian monarchs continued to selectively dictate government policies until King William IV dismissed Lord Melbourne in 1834.
Countries like Liechtenstein and Monaco allow ruling monarchs to wield significant executive power while remaining liberal democracies rather than undemocratic states. Hereditary Prince Alois of Liechtenstein threatened to veto a possible approval of a referendum to legalize abortion in 2011 after not vetoing any law for over 30 years.
During the 1975 Australian constitutional crisis, Governor-General dismissed Prime Minister Gough Whitlam on the 11th of November 1975 when the Senate threatened to block the Government's budget. Fifteen constitutional monarchies exist under King Charles III known as Commonwealth realms which share the same person as their hereditary monarchy.