The salute of the Confederate lieutenant is a contemporary version, with the back of the hand facing outward and angled down. During the Civil War period the salute was much like the British, open palm faced outwards.
The flag suspended in the Confederate general's office represents the Confederate navy, not the army.
Virginia is wearing brassard with the Red Cross emblem. Such a device would not be worn yet by American medical personnel, even in the Union Army. What surgeons wore on their uniforms was a green tab with the emblem caduceus. Nurses wore no devices.
One of the Confederate soldiers is carrying a Winchester Model 1866 (with its distinctive brass receiver), a gun that was not available during the Civil War.