I don't think that there's any definite way to tell the age, but you can get an approximate idea by counting the growth rings (ridges) around the scutes.
The only way to tell the gender is by their tails. Males have bigger, longer tails with a hook on the end, and the cloaca looks like a slit. Females have smaller tails with a cloaca that looks like an asterisk *. In other species of tortoises the males have a curved plastron, but Russians don't. So sometimes vets will see a male Russian with a flat plastron and will tell you he's a girl. The tail is the only way to tell.
Here's a link to some pictures of male and female Russians.
http://russiantortoise.org/male_female.htm
Aug 01, 2009
Tortoise age and sex by: Shelly
The only way to be really sure how old a tortoise is is to be there when it hatches. Since you probably weren't there, size can tell you whether your tortoise is full grown or just a baby or something in between. A full grown Russian will be 4 to 8 inches long.
As for sexing a tortoise, I made a page about that.