Strange behavior for a pointer of an interface

I wrote 3 similar functions to figure out a strange behavior of Go's pointer reflection.

package main

import (
    "reflect"
    "fmt"
)

var i interface{} = struct {}{}     // i is an interface which points to a struct
var ptr *interface{} = &i           // ptr is i's pointer

func f(x interface{}) {             // print x's underlying value
    fmt.Println(reflect.ValueOf(x).Elem())
}

func main1() {  // f is asking for interface? OK, I'll use the struct's interface
    structValue := reflect.ValueOf(ptr).Elem().Elem().Interface()
    f(structValue)
}

func main2() {  // Error? Let me try the struct's pointer
    structPtr := reflect.ValueOf(ptr).Elem().Interface()
    f(structPtr)
}

func main3() {  // Why this one could succeed after New() ?
    typ := reflect.ValueOf(ptr).Elem().Elem().Type()
    newPtr := reflect.New(typ).Elem().Addr().Interface()
    f(newPtr)
}

func main() {
    //main1()   // panic: reflect: call of reflect.Value.Elem on struct Value
    //main2()   // panic: reflect: call of reflect.Value.Elem on struct Value
    main3()     // OK. WHY???
}

Only main3 is working, the other 2 would panic. Why? The key difference of 3 is that it creates a New Value.

As to main2, I think ValueOf().Elem().Interface() has already reconstructed a interface which points at the struct{}{}, just don't understand why it would fail.