Well, I'm not sure about the Tiara-Question.
I guess it is like in Denmark!
When Sonja was a Crown Princess she wore all Tiaras she wears as a Queen, too. She didn't only wear 1 or 2 ,like Mette and Mńrtha do.
The main difference between Sonja and Mette-Marit as Crown Princesses is that Sonja wasn't only the Crown Prince's wife , but also Norway's First Lady (because King Olav's wife Mńrtha died before she became Queen.And so the Crown Princess Sonja was Norway's first Lady).
It seems the Emeralds and Diamond Tiara are only used by Norway's first Lady: Before the marriage of Harald, his older sister Astrid was Norway's 1st lady and she also wore the Diamond Tiara and the Emerald Parure.
When Sonja became CP Astrid didn't use them anymore.
So my guess: We have to wait until MM becomes Queen until we'll see her with new Tiaras.