Boj Olaneta 01212601 Knife Sharpener, ceramic, Silver

One review said that they sharpened a knife under running water. Is that needed? Does it come with instructions?

What is the sharpening angle 15 or 20 degrees?

Would this be a good gift for someone who doesn’t know anything about sharpening knives?

Sirve para todo tipo de cuchillos ? de acero inoxidable ? cuchillos sierras?