Marimo moss balls tend to come 1.5 to 2 inches in diameter and will grow, but very slowly about 1/4 inch per year so you can use the size to estimate its age. In the wild they can get 8 to 10 inches in diameter so they can live decades.
They are also sold as nano versions, i cant tell from the link what type of moss ball it is. I dont speak greek. I presume a nano moss ball is just a younger moss ball that will grow.
You can split a moss ball. Cut it in half, roll the halves into spheres and tie some thread around so it maintains its shape. There are youtube videos of this.
Moss balls can also reproduce, budding off new balls.
Looking up some stuff, some people keep them as pets, particularly in japan. Ideal first pets for young children.