[SPOILERS]
To get into kitchens - Wear maid outfit and talk to maid in left hand screen.
To get past moustache men - wear Powdery Wig and talk to woman scrubbing floors in the barracks (red room) to get giant moustache. Wear giant moustache and talk to moustache men.
To talk to the princess- pick up punch from the banquet hall from the giant punch bowl. Give this drink to her guard.
Answers to princess quiz ->
1. She likes to dance
2. She's nicer than she lets on (talk to woman in the banquet hall standing near pillar of gifts)
3. Any answer (correct answer needs to be unlocked)
Go talk to Emeric while wearing the livery. Ask him about the princess' nickname.
Go back to princess and give this answer as the final question in her quiz.
After that talk to the guard in the right hand side of the screen.
That's it! You'll get the ending after that.