Inheritance: Function that returns self type?

You can use CRTP, the curiously recurring template pattern:

template<class Derived>
class A {
public:
    Derived* Hello() {
        return static_cast<Derived*>(this);
    }
};

class B : public A<B> {
public:
    B* World() {
        return this;
    }
};

   
int main() {
    B test;
    test.World()->Hello();
    test.Hello()->World();
}