I haven't had any problems, but my game did just update today. Maybe that's causing the problem?

Have you tried doing the same quests multiple times? I know that works with some things. If you haven't tried it yet, maybe give it a go and see if it works :)

Hi, I believe the background you are referring to is the Cruising Devil background. As far as I know, this background can only be gotten from buying the one time 1 USD sale (you also get 100 diamonds and 30000 gold). You can also get backgrounds from other suits or events, such as the Pink Wishes suit that you get for connecting to Facebook. This suit gives you the Memorial Day background. Hope this helps!

And yes, for the princess stages, I just do the same quest in maiden following momo's tips, and then do the princess stage and just use my last suit. That way I don't have to go looking twice, or have to worry about forgetting a piece. ;)