Not sure about the greeting... Are you sure the Quest Priority is set high enough (something else may be over-riding it, if not), and is it assigned to this NPC? Also check your Conditions-- you may have accidentally set an impossible condition for it.
For Yes and No options, you will need to make two new topics:
- MyQuestAnswerYes
- MyQuestAnswerNo
(Note that these names can be anything, I'm just simplifying it
)
You then need to add in your text for the NPCs response like you did before. Now, return to your original line of Dialouge. Let's assume your NPC says "Will you do the Quest for me?", that is the line you would need to go to.
Look to the right-side of the Dialogue area, about mid-way up from the bottom. There's two boxes: AddTopic and AddChoices-- right-click in AddChoices, and select "NewTopic".
From here, select the two topics you made above.
They are now set as choices to the Dialogue, and will be the only responses available immediately after the NPC has spoken, if done correctly