Margies have triangular spots on the plastron and one stripe mark on the tail. Getting older they develop a skirt. Old females have flexing plastron. Greek tortoises have spurs. Hermanns have spur tails and yellow cheeks (western subspecies).
Lol. Tortoises live on the ground but not on the bark chips. Topsoil is a much more natural substrate. An open-top setup is not suitable for margies because they live in a quite humid climate. They want a dry substrate and humid air. A wet chamber is a must.
My marginated tortoise spent last winter at 19-20C. I believe it is a minimum acceptable temperature if you don't want to hibernate it. If you will go below that temperature, your tortoise will fall asleep every single day. It is quite stressful.