Russians do go by another name, Horsfield tortoise.
They're the smallest commonly kept and come from an arid environment. In the wild they do hibernate, and if possible it's best to allow this behavior in captivity.
The first year after getting the tortoise it's suggested that you do not allow them to hibernate, this is to make sure they're healthy. Sick or underweight torts can die. To prevent hibernation you keep them inside for the winter, provide at least 12 hours of light, and keep the temperature range up as required per species.
Greek tortoise (testudo graeca) are also called Mediterranean Spur Thighed tortoise or just Mediterranean tortoise.
Horsfield and Greek tortoise are both from the family testudinidae - european tortoises, which also includes marginated and hermann's (hermann's hibernate). There are also a lot of subspecies within testudo graeca, as well as two subspecies within Testudo hermanni, western hermann's and eastern hermann's(larger of the two).
Red foot's are a South American tortoise. They do not hibernate and would need to be wintered inside. Adult size is around 14 inches.
Sulcata or African spurred tortoise reach 18 inches, largest recorded - 30 inches. They are a desert species and do not hibernate, again that means wintering them inside. Weight for an adult is actually closer to 70-100lbs, again largest record is huge - 240lbs .
All of these tortoises do best if provided with an escape proof and predator proof pen. This means burying the fencing or wire mesh under it at a dept of 2 feet or more. Availability to natural, edible grasses helps as well since tortoises do graze, and grass provides the high fiber needed. Natural sunlight is also much better then artificial reptile UVB bulbs.
Hatchlings grow fast compared to their overall lifespan, but growth rate is dependent on diet. More protein = faster, but not exactly healthy growth. Plan pens for adult size or be willing to add to the pen in a couple of years.
I suggest you stick with an european tortoise, preferablly a species that hibernates if you do not want to provide a large indoor enclosure for it every winter. Up to 6x6 foot is a lot of space.
Reptile bulbs are also very expensive, the mercury vapor which are best for providing uvb and heat that tortoises need to bask in cost around $60 per bulb, but do have a higher uvb output and longer life than florescent tubes.
All reptiles need UVB or vitamin D3 to process calcium. For diurnal species it's best to let them process as much of the D3 needed from uvb. Without this they get metabolic bone disease, misshapen shells and soft bones. You'll also need to supplement with calcium, calcium w/D3, and a multivitamin, on a schedule. Hatchlings of course need a lot of calcium for growth.
So in the long run, relying on nature to provide sunlight is best.
Pens need to be large, minimum of at least 6x6' for adults but bigger is better if you can build it and make it safe. Sulcatas and red foots, of course need larger pens. Definitely have a lid over the pen if you're getting a baby, even a cat can take off with a baby tortoise in it's mouth.
Diets are different for most, but general - no meat (this includes canned dog and cat food) and no bananas (binds calcium), generally no or little fruit as this processes to sugar too easily and can upset their digestive tract.
I think I covered most of the basics?
Too much time on my hands to read and study this stuff.
I will admit I do not own a tortoise (but certainly plan to in the future
), most of the information is from reading up on box turtle care that is most commonly found on tortoise sites, some care and requirements are similar as well. Since I'm usually looking on the tortoise sites already I figure "might as well read this too", I'm a bit of a human sponge for info and facts.