I've read the Constitution. Any agreement with a foreign power requires consent of Congress.
Yep. Article IV covers admission of states and changes in status, including removing a state from the Union through splitting or combining.
Hereditary would be illegal if the state was still in the union, but an elected monarch for life would not (Hamilton argued for an elected monarch in convention). A 'republican' government is one where the people are represented by elected officials.
Sure it would. Titles of nobility are forbidden by the Constitution.
Nonsense. There is no clause stating that the ratification is permanent or perpetual, or that permission must be sought to leave. Forget 'implicit' powers, the states possess EVERY power not delegated to the federal government and not prohibited to the states.
Ridiculous. The Constitution reserves powers to the United States, and some of those may be implied from the Constitution.
Nope. Only the admission of a new state, or the creation of a new state within an existing state, or from merger of two states, or a new state from parts of existing states. It is absolutely silent about a state reducing it's borders or removing itself from the union.
Titles of nobility are forbidden by the Constitution.
Please note, my comment indicated the "monach" was elected, not hereditary titled.
The Constitution reserves powers to the United States, and some of those may be implied from the Constitution.
Wrong. The Constitution reserves "delegated" (capable of being resumed) powers to the states, not to the federal government.