Monarchs are not allowed to unilaterally abdicate; the only monarch to voluntarily abdicate, Edward VIII (1936), did so with the authorisation of a special Act of Parliament.
It is the prerogative of the monarch to summon, prorogue, and dissolve Parliament.
The monarch is only an ordinary member, and not the head or leader, of the established Church of Scotland; however, he or she does hold the power to appoint the Lord High Commissioner to the Church's General Assembly.
Most medieval historians would argue that the existence of France proper did not begin until the advent of the Capetian Dynasty in 987, or, at the very earliest, with the establishment of the Kingdom of Western Francia at the Treaty of Verdun in 843.
By 1453, however, the English had been expelled from all of France save Calais (and the Channel Islands), and Calais itself fell in 1558.
Nevertheless, Englishmonarchs continued to claim the title until the creation of the United Kingdom in 1801.