According to my notes, the 2nd Georgia Cavalry Reserves was an alternate designation for Dorough's Georgia Cavalry Regiment (Col. Thomas T. Dorough, Lieut.Col. J. Bee Eberhart, Maj. W. B. Pruitt). This was a late war outfit authorised in September 1864 to be attached to Col. Jesse A. Glenn's brigade of reserve cavalry. The regiment is also referred to as the 2nd Regiment, Glenn's Cavalry. The field officers are mentioned in the Southern Watchman newspaper for 2 December 1864. The 1st Georgia Cavalry Reserves was Col. James Bryan's Georgia Cavalry Regiment (aka 1st Regiment, Glenn's Cavalry). I have no information on a 3rd Georgia Cavalry Reserves.