1

Where should I type this line into this shader file.

var shader = Shader.Find(“Hidden/CubeCopy”);

Shader "Hidden/CubeCopy" {
	Properties {
		_MainTex ("Main", CUBE) = "" {}
		_Level ("Level", Float) = 0.
	}
	CGINCLUDE
	#pragma vertex vert
	#pragma fragment frag
			
	#include "UnityCG.cginc"

	float _Level;

	struct v2f {
		float4 pos : SV_POSITION;
		float4 uvw : TEXCOORD0;
	};

	v2f vert(appdata_base v)
	{
		v2f o;
		o.pos = mul(UNITY_MATRIX_MVP, v.vertex);
		o.uvw = v.texcoord;
		return o;
	}

	UNITY_DECLARE_TEXCUBE(_MainTex);

	float4 frag(v2f  i) : SV_Target
	{
		return UNITY_SAMPLE_TEXCUBE_LOD(_MainTex, i.uvw.xyz, _Level);
	}
	ENDCG
	SubShader {
		Tags { "RenderType"="Opaque" }
		LOD 200
		Pass {
			ZTest Always
			Blend Off
			AlphaTest off
			Cull Off
			ZWrite Off
			Fog { Mode off }
			CGPROGRAM
			#pragma target 3.0
			ENDCG
		}
	}
	SubShader {
		Tags { "RenderType"="Opaque" }
		LOD 200
		Pass {
			ZTest Always
			Blend Off
			AlphaTest off
			Cull Off
			ZWrite Off
			Fog { Mode off }
			CGPROGRAM
			#pragma target 2.0
			ENDCG
		}
	}
	Fallback "Diffuse"
}

Any solution to these appreciated here!

2

That is C# line. You can put that into your C# monobehaviour script. Not into the shader code.

3

That line doesnt go in the Shader.

You use it to Find your shader of the same name when setting up a Material