Returning interface pointer from a COM component

I have a basic question about returning interface pointer from a COM
component, to caller. I provided these samples to just to be clear.
This came to light because CSimpleMap<BSTR, BSTR>, stored in innermost
object(say ILevel4) started loosing data. Then I replaced it with
std::map<wstring,wstring> and started returning interfaces pointer
doing QI(). Please see below, give your thaoughts, these questions
have been nagging me for a while. I hardly comeacross a COM example
that implements nested objects.

_ATL_INTERFACE_DEBUG ignores the interface pointer, returned to
client, generated without calling QI(),

CFirstObject :: FinalContructor()
{
     //Here I create the encapsulated COM object
     CComObject<CLevel1>::CreateInstance( &m_objILevel1);
}

STDMETHODIMP CFirstObject :: GetLevel1( ILevel1** ppL1)
{
      //Returning to Interface pointer: Which one is among these is
correct.
     a)
         ILevel* pLevel1;
           m_objILevel1->QueryInterface(IID_ILevel1, (void**)ppL1 );
          (*ppL1)->AddRef();

          pLevel1 = (*ppL1);

     b)
          *ppL1 = (ILevel1*)m_objILevel1;
          (*ppL1)->AddRef();

     //Calling interface method from inside
       a)
            m_objILevel1->DoSomething();
       b)
            pLevel1->DoSomething();
}

class ATL_NO_VTABLE CLevel1 : public IDispatchImpl<ILevel1
{
   ...........
   STDMETHOD(DoSomething)(BSTR);

    HRESULT NonInterfaceMethod(); .......
};

class ATL_NO_VTABLE CFirstObject : public IDispatchImpl<IFirstObject
{
  ...
  CComObject<CLevel1> m_objILevel1;

   STDMETHOD(GetLevel1)(ILevel1** ppL1);
};

Thanks
Ramesh