About the special: https://www.youtube.com/watch?v=u_5O44DnjIY (https://www.youtube.com/watch?v=u_5O44DnjIY)
The special itself: https://www.youtube.com/watch?v=KLze3jfaK00&t=159s (https://www.youtube.com/watch?v=KLze3jfaK00&t=159s)
Both links say that the videos are not available any more :bluesad:
I can understand the special disappearing, but not the review. Can't find the review anymore, but here's a few links with background info:
https://www.animecharactersdatabase.com/source.php?id=103438 (https://www.animecharactersdatabase.com/source.php?id=103438)
https://movie.douban.com/subject/26235583/ (https://movie.douban.com/subject/26235583/)
https://www.nautiljon.com/animes/niji+no+kanata+e (https://www.nautiljon.com/animes/niji+no+kanata+e)!+shoujo+diana+monogatari.html
https://www.reddit.com/r/ObscureMedia/comments/o4alaq/a_princess_diana_anime_1986/ (https://www.reddit.com/r/ObscureMedia/comments/o4alaq/a_princess_diana_anime_1986/)
The special itself is titled 虹のかなたへ! 少女ダイアナ物語 if you want to search for it; should still be online somewhere.