Surface Shader not working when using Vertex Lit render settings?

Hi, Firstly yes I am new to the world of shaders, I have just about got my head around writing surface shaders but for some reason non of my shaders are rendering when the camera is set to vertex lit?

I have had a read around and think i now need to move onto fixed function shaders which seems a totally different shader language?

Is it true that surface shaders just wont work on vertex lit or is it down to the lighting set up and therefore can be configured to work in both set ups?

Thanks for any advice given I'm looking to learn and progress!

Here is the shader im working with:

 Shader "Custom/UV2AlphaMask" {
     Properties {
         _MainTex ("Base (RGB)", 2D) = "white" {}
         _AlphaMask ("Alpha Mask (A)", 2D) = "white" {}
         _AlphaAmt ("Alpha Amount", Range(0,1)) = 0.5
     }
     SubShader {
         Tags { "RenderType"="Transparent"  }
         LOD 200
         
         CGPROGRAM
         #pragma surface surf Lambert alpha
 
         sampler2D _MainTex, _AlphaMask;
         fixed _AlphaAmt;
 
         struct Input {
             float2 uv_MainTex, uv2_AlphaMask;
         };
 
         void surf (Input IN, inout SurfaceOutput o) {
             half4 c = tex2D (_MainTex, IN.uv_MainTex);
             half4 mask = tex2D (_AlphaMask, IN.uv2_AlphaMask);
             o.Albedo = c.rgb;
             o.Alpha = mask.a * _AlphaAmt;
         }
         ENDCG
     } 
     FallBack "Diffuse"
 }
 

update

As an example I found this shader as part of the unity default terrain shaders, is anyone able/willing to explain a little about how come this seems to be a mix of both surface shader and fragment shader? and possibly a nudge in the right direction for further investigation?

Thanks,

 Shader "Hidden/TerrainEngine/Details/Vertexlit" {
 Properties {
     _MainTex ("Main Texture", 2D) = "white" {  }
 }
 SubShader {
     Tags { "RenderType"="Opaque" }
     LOD 200
 
 CGPROGRAM
 #pragma surface surf Lambert
 
 sampler2D _MainTex;
 
 struct Input {
     float2 uv_MainTex;
     fixed4 color : COLOR;
 };
 
 void surf (Input IN, inout SurfaceOutput o) {
     fixed4 c = tex2D(_MainTex, IN.uv_MainTex) * IN.color;
     o.Albedo = c.rgb;
     o.Alpha = c.a;
 }
 
 ENDCG
 }
 SubShader {
     Tags { "RenderType"="Opaque" }
     Pass {
         Tags { "LightMode" = "Vertex" }
         ColorMaterial AmbientAndDiffuse
         Lighting On
         SetTexture [_MainTex] {
             combine texture * primary DOUBLE, texture * primary
         } 
     }
     Pass {
         Tags { "LightMode" = "VertexLMRGBM" }
         ColorMaterial AmbientAndDiffuse
         BindChannels {
             Bind "Vertex", vertex
             Bind "texcoord1", texcoord0 // lightmap uses 2nd uv
             Bind "texcoord", texcoord1 // main uses 1st uv
         }
         SetTexture [unity_Lightmap] {
             matrix [unity_LightmapMatrix]
             combine texture * texture alpha DOUBLE
         }
         SetTexture [_MainTex] { combine texture * previous QUAD, texture }
     }
 }
 
 Fallback "VertexLit"
 }