I have played it through a few times, allways with a walkthrough, the keyboard puzzle SUCKS, but a good walkthrough will explain how to count the notes on the sliders.
Riven is brilliant, but still need a walkthrough to finnish it, I have the official guide book to Riven, and it has damn well helped me a lot.
Myst III was never made by Cyan, but by Presto, and while very similar to the original games, it has a different feel.
Myst IV was made by Cyan, and in terms of story I find it lacking, especially the spirit puzzle was a mistake, there is also too much live action for my taste, but the environments are beautiful and the visual quallity of the game is fantastic.
Myst V is a major departure from the rest of the games, both in terms of story and visual quallity. The story is about the end of Dn'i, and setting a slave race free, I never got into it, the visual design is made in a full 3D engine and looses the gorgeous visuals of the last game.
URU was a side project where Cyan tried to make a Myst themed MMORPG, where you travel to the cleft and start your own Myst adventure, the idea was that people would meet up and go to adventures together, but it never got off the ground.
Myst Online is an effort by the fan community and Cyan to make the URU live portion work, and is currently free to play.
Myst 2021 is a complete remake of Myst in the Unreal engine, the game looks fantastic and can even be played on iOS and in VR with the Quest.
Cyan has had a few other large impact releases:
Obduction: a sci-fi adventure puzzle game where you are abducted into an alien world and have to solve a mystery with a lot of puzzles, fantastic graphics.
Firmament: another sci-fi adventure puzzle game, where you explore worlds with weird technology, I don't know that much about it despite having played it on release last year.
Fun fact since Myst has been released so many times over the years it has a huge list of supported platforms:
Mac OS
Sega Saturn
Sony Playstation
3DO
Microsoft Windows
Atari Jaguar CD
Philips CD-i
AmigaOS
Pocket PC
Playstation Portable
Nintendo DS
iOS
3DS
Android
Oculus Quest
Quest 2
Nintendo Switch
Xbox One
Xbox Series X/S