Proper way of casting for a method reference parameter - c++

Question

I have an array of objects stored. I want to reach them. The below code works just fine:
class Primitive
{
public:
int SomePrimitiveValue = 5;
};
class Derived : public Primitive
{
public:
int SomeDerivedValue = 8;
};
Primitive * ExtractTheLast()
{
if (FCount > 0)
{
Primitive * result = *((Primitive**)((char*)FData + (FCount - 1 * TypeSize())));
RemoveByIndex(FCount - 1);
return result;
}
return nullptr;
}
int main()
{
Derived * result = (Derived *)ExtractTheLast();
if (!result)
result = new Derived();
}
but I want to see if this access operation ExtractTheLast is successful so I modified the code such as;
bool ExtractTheLast(Primitive *& lastItem)
{
if (FCount > 0)
{
lastItem = *((Primitive**)((char*)FData + (FCount - 1 * TypeSize())));
RemoveByIndex(FCount - 1);
return true;
}
lastItem = nullptr;
return false;
}
int main()
{
Derived * result = nullptr;
if (!ExtractTheLast((Primitive*&)result))
result = new Derived();
}
In this code ExtractTheLast((Primitive*&)result) doesn't worked as I intended, my guess is compiler converting or maybe treating the content data of the class as it is Primitive and returns a broken object.
My question is how can I properly type cast inside a method's parameter zone? and I really don't want to use templates like ExtractTheLast<Derived>().
-------------------EDIT---------------------
After i realized my question is not clear enough, i try to summerize it but couldn't create the same result as in my project so i decided showing two way which first one works but the second one gives funny resluts.
Please bare in mind that i only want to know the difference between those two line of codes
(RenderRequestO *)Requests_idle->GetTheLast()
and
Requests_idle->GetTheLast((PrimitiveO*&)result)
one of them returns the object directly and other one returns it as parameter and i think when i try to type cast inside the parameter block, compiler gives wrong result.
this is the code works fine:
MutexLock(mutex);
RenderRequestO * result = Requests_idle->Count() > 0 ? (RenderRequestO *)Requests_idle->GetTheLast() : new RenderRequestO();
if (Requests_idle->Count() > 0)
Requests_idle->RemoveLast();
...
..
and this is the code doesn't work as i want it to be:
MutexLock(mutex);
RenderRequestO * result = nullptr;
if (!Requests_idle->GetTheLast((PrimitiveO*&)result))
result = new RenderRequestO();
...
..
if i get the related object such as (RenderRequestO *)Requests_idle->GetTheLast() it works fine but if i get try to get it like Requests_idle->GetTheLast((PrimitiveO*&)result) it returns an object but its derived fields are all inaccessable (when i move my mouse over it intellisense says "unable to read memory")