The excerpt mentions central government and the states but does not speak (except by mentioning) of executive branch or amendments, so we reject options 2) and 4).
Among options 1 and 3: 3 speaks of central government having the power over the states, which is the opposite of what the text says: it stresses how much power should stay with the states.
So the correct option is 1)
I believe they were called unionists as they were part of the Union. The south was the Confederacy therefore southerners were Confederates.