Thank you for compiling this guestlist.
Belgium - Princess Astrid and Prince Lorenz are HRH rather than HIRH. A recent example from the Belgian monarchy's homepage:
Concours Reine Elisabeth – Violon 2019
30 avril 2019 (Jour entier) - 06 juin 2019 (Jour entier)
[…]
Leurs Altesses Royales la Princesse Astrid et le Prince Lorenz assisteront à une session de la finale le vendredi 24 mai 2019 au Palais des Beaux-Arts de Bruxelles.
https://www.monarchie.be/fr/agenda/concours-reine-elisabeth-violon-2019
(Translation:
Their Royal Highnesses Princess Astrid and Prince Lorenz will attend a session of the finals of the finals on Friday, May 24 at the Palais des Beaux-Arts in Brussels.)
Denmark/Greece - Anne-Marie would be representing Denmark only, as Greece stripped their former royal family of their status and considers them to be private citizens.