Sorry, but this is not a photo of 1906, but 1914 and later. Нe has four crosses of St. George (a full St. George knight), but in addition he has St. George medals, which began to be issued only in 1913.
Most likely, this photo is more likely from 1917-19. Made after returning from the front of the Great War (WWI). He is not wearing a field uniform, but the usual clothes of the Cossacks. On the shoulder straps there are no monograms denoting his regiment. Possibly (not exactly) made when he was in the White Army during the Russian Civil War in 1918-1920.
His military rank is senior sergeant (starshy uryadnik).
It is extremely difficult to identify a Don, Kuban, Amur or Ural Cossack. They were distinguished by the color of the stripes on the trousers and the band of the cap. This is not visible in the black and white photo.
The photo is not reverse, as indicated by the position of his awards: first crosses, then medals. It is right. Edged weapons were carried on the left side (this is a shashka, not a saber). The "wedding ring" is just a defect in the photo.
For comparison: young Cossack (WWI) in a field uniform with his wife http://s42.radikal.ru/i095/1301/a8/73fa709f2fa4.jpg