But at the time, Virginia by its own choice, was not part of the United States. Once WV was formed, Lincoln and Congress granted it statehood. To argue the right or wrong of these actions is like a chicken or the egg controversy.
A lot of people in WV remained loyal to Virginia and fought on the Confederate side...One of them was Stonewall Jackson, who was a native of what became WV although a resident of Lexington, VA (he died before WV was officially admitted as a state).
No, it isn't. By their own theory, Virginia was still part of the Union, and Virginia did not give her consent to partition. Ergo the partition of Virginia was flatly unconstitutional, then and now.
Nothing to the contrary whatsoever withstanding.
Lincoln always contended that the Confederate States were "in rebellion" but still part of the United States. That's why he refused to allow the number of stars on the flag to be reduced.