How to write shaders in Unity more efficiently?

Question

Unity

There were tasks to write several shaders for Unity for mobile phones. Starting to google, I came across a huge amount of unstructured information in which I simply got lost. Could you answer a few questions? :)

1. Is Shader Graph suitable for writing optimized shaders for mobile phones?
2. Everyone writes that the CG language is outdated, but Unity uses it. Is it worth it to study it?
3. If on mobile phones OpenGl and not DirectX, isn't it better to write in GLSL?
4. CG and HLSL - the same thing?
5. What road map do shaders have? Where to start studying?
6. Unity has Surface Shaders. Are they worse than fragment or vertex ones?

Answer 1

Shaders and effects in Unity. Recipe Book by Kenny Lammers
May help.