Nice yard you have there, but I think you are looking for a bigger tortoise than a russian tort. Russian torts are only 5 to 6 inches.
Russians are very active torts and will use all the space you give them. The more the better.
All torts have UVB and heating requirements. They are cold blooded and must have external heat to be active and digest food. The sun is the best source of both and Russians do very well outdoors as long as the sun shines.They have uvb lighting and heating requirements.
They eat a wide range of greens. You are correct that they should not eat fruitThey do not eat vegetables or fruit, but only certain greens and weeds.
It is true that any outdoor enclosure should be predator proof. Which predators you have depends on your location. Many keepers use a nightbox to keep their torts safe overnight outdoors. There are examples in the Enclosures forum.My tort has never hybernated. He has never been outside overnight in his enclosure because we have possums and raccoons that will eat him during night hours. He spends nights and winters inside, protected. Only during hot summer days will I put him out in his enclosure, but then returning him back inside by late afternoon