Tshax, if you're struggling with Question 3, try to get hold of "C++ GUI Programming with Qt 4, Second Edition" by Jasmin Blanchette; Mark Summerfield. It helped me a lot.
I'm done with part A only. Had some trouble passing the values from the dialog to the main window in Question 3. If it is of any help here is how I did it:
Dialog* d = new Dialog(this);
if (d->exec() == QDialog::Accepted) {
result->setText(d->getAnwers());
}