Nonsense. There's no agreement to "abide by the provisions of the Constitution" anywhere. It does state that the 'Ratification of the Conventions of nine States, shall be sufficient for the Establishment of this Constitution between the States so ratifying the Same.' So, implicitly, the convention of a state can withdraw it's ratification. Forget implicit, the Constitution EXPLICITLY states, 'Full Faith and Credit shall be given in each State to the public Acts, Records, and judicial Proceedings of every other State.'
They were admitted by a vote of Congress.
The originial states were not. And SCOTUS has repeatedly held that the latter additions were admitted as equals of the original states.
And the Constitution EXPLICITLY states the Constitution will be the supreme law of the land, "...any Thing in the Constitution or Laws of any State to the Contrary notwithstanding." So when the public acts, records or judicial Proceedings violate the Constitution then full faith and credit are not warranted.
The originial states were not. And SCOTUS has repeatedly held that the latter additions were admitted as equals of the original states.
The later states were admitted under the provisions outlined in the Constitution, which was adopted by the original 13 states when they ratified it.