How could the federal government tell state governments how they should use their land for anything, much less defense? Which was a federal responsibility anyway.? The federal government could not and did not own state land.
No, they owned federal land. In the case of Fort Sumter it was land that was deeded to the federal government by act of the South Carolina legislature.
The blockades at Pensacola and Charleston predated 4:15 a.m. April 12, 1861.
If I remember correctly the Sumter relief force met a ship leaving Charleston (the Nashville?) and it was allowed to proceed. Some time prior to that the Confederate batteries fired on the Rhoda Shannon as she entered the port. No doubt there was other traffic in and out other than those two. So how could Charleston be blockaded if ships were coming and going?
You misread my comment.
The blockade began when the Harriet Lane's cannon fire turned shipping away from Charleston docks on the evening of the 11th.