Look here for the first hint
Which etiquette manners are being represented in the pictures?
Look here for the third hint
The answer is a 3 digit code
Look here for the second hint
Which numbers from the 9 most common etiquette manners are being presented in the pictures?
Look here for the fourth hint (spoiler)
The first picture shows etiquette manner 4
The second picture shows etiquette manner 1
The third picture shows etiquette manner 8