Need help with Sprite shadow shader!!!

Hello everyone! I'm having a problem with my project. Again shaders are killing me XD So I need a Sprite shader that is: - Unlit - Transparent ( so for example the image is a blue circule with the rest with alpha = 0, the alpha part needs to be transparent) - Only recieve shadows - It needs to have a property color that allow me to change the overall alpha to make a fading effect (shown in the image 3 as a gif).

I have a shader that accomplishes everything except the fading effect. I was wondering if someone could fix this one for me since I have 0 knowledge of shaders XS.

The Sprite/Default shader accomplishes everything except receiving shadows like image 1 (shown in image 2).

The one I already have was given to me by another user.

 // Upgrade NOTE: replaced 'mul(UNITY_MATRIX_MVP,*)' with 'UnityObjectToClipPos(*)'
 
 Shader "UnlitShadows/UnlitShadowReceive" {
     Properties{
         _MainTex("Base (RGB)", 2D) = "white" {}
 _CutOff("Cut off", float) = 0.1
     }
 
         SubShader{
         Pass{
         Tags{ "LightMode" = "ForwardBase" }
         CGPROGRAM
 #pragma vertex vert 
 #pragma fragment frag 
 #include "UnityCG.cginc" 
 #pragma multi_compile_fwdbase 
 #include "AutoLight.cginc" 
         sampler2D _MainTex;
     float4 _MainTex_ST;
 uniform float _CutOff;
     struct v2f {
         float4 pos : SV_POSITION;
         LIGHTING_COORDS(0,1)
             float2 uv : TEXCOORD2;
     };
 
     v2f vert(appdata_base v) {
         v2f o;
         o.pos = UnityObjectToClipPos(v.vertex);
         o.uv = TRANSFORM_TEX(v.texcoord, _MainTex);
         TRANSFER_VERTEX_TO_FRAGMENT(o);
         return o;
     }
 
     fixed4 frag(v2f i) : COLOR
     {
     float4 color = tex2D(_MainTex, i.uv);
         if(color.a < _CutOff) discard;
 
         float attenuation = LIGHT_ATTENUATION(i);
     return color * attenuation;
     }
         ENDCG
     }
 
         Pass{
         Blend One One
         Tags{ "LightMode" = "ForwardAdd" }
         CGPROGRAM
 #pragma vertex vert 
 #pragma fragment frag 
 #include "UnityCG.cginc" 
 #pragma multi_compile_fwdadd_fullshadows 
 #include "AutoLight.cginc" 
         sampler2D _MainTex;
     float4 _MainTex_ST;
     uniform float _CutOff;
 
     struct v2f {
         float4 pos : SV_POSITION;
         LIGHTING_COORDS(0,1)
             float2 uv : TEXCOORD2;
     };
 
     v2f vert(appdata_base v) {
         v2f o;
         o.pos = UnityObjectToClipPos(v.vertex);
         o.uv = TRANSFORM_TEX(v.texcoord, _MainTex);
         TRANSFER_VERTEX_TO_FRAGMENT(o);
         return o;
     }
 
     fixed4 frag(v2f i) : COLOR
     {
         float4 color = tex2D(_MainTex, i.uv);
         if(color.a < _CutOff) discard;
         float attenuation = LIGHT_ATTENUATION(i);
     return color * attenuation;
     }
         ENDCG
     }
     }
         Fallback "VertexLit"
 
 }

image 1: Provided shader - dont work with fading effect.

image 2: Sprite Default shader - dont work with shadows

image 3: Fading effect using Sprite Default

So basically I need to transform the Sprite / Default shader so it can receive shadows, without changing its behaviour