new KeyWord c++ (Assistance Required)

1. I have following code that work 100 percent fine. I am also aware, what is actually going behind the scene. how "new" works in that case.

   struct ABC{
       int data = 1234;
   };
   ABC *obj = new ABC;
   cout << "obj->data";
   
   

2. The following code does not work it compiles correctly then crashed. no syntax or compile error.

   struct ABC{
       int data = 1234;
   };
   ABC *obj; // please explain??
   cout << "obj->data";
   
   

3. Following code also works fine and simple one.

   struct ABC{
       int data = 1234;
   };
   ABC *obj, myobj;
   myObj = &obj;
   cout << "obj->data";
   
   

I am also aware, hows 3^rd one is working. Please explain, why 2^nd one is not working. Sorry for not making main() procedure.