You can feed hibiscus flowers and leaves to your tortoise, but make sure it isn't Flower-of-an-Hour (Hibiscus trionum). According to the Tortoise Table, there is no evidence yet about Flower-of-an-Hour being edible to tortoises, and it is toxic to goats and other animals.
Is it mandatory to brumate Russian tortoises? I haven't brumated my Russian tortoise last winter and I was wondering if that will have an impact on his health.