Why do these games not have their own hub on the website?
Because we have not played through them thoroughly enough to cover them in the same detail as the main games. One honest page is better than eight empty ones. Once we have played through one of them, it will get its own hub and this page will link to it.
Are they part of the series' story, or are they spin-offs?
They are part of it. All four take place in the same worlds as the main games, and three are direct prequels — Advance and Liberty City Stories to GTA III, and Vice City Stories to Vice City. Chinatown Wars takes place in the same Liberty City as GTA IV.
Which one is most worth playing?
This is our opinion, not a fact: Chinatown Wars for how differently it looks and plays, and Vice City Stories for the empire building that never returned. Advance is more interesting from a historical perspective.
Can any of them be played on PC?
None officially. Liberty City Stories and Chinatown Wars run on mobile through a GTA+ subscription; the others remained on the consoles for which they were released.
Why does GTA Advance look like GTA 2?
Because it ran on Game Boy Advance, where a three-dimensional city was not possible. Digital Eclipse therefore returned to a top-down view. It has no story connection to the old games, however — it belongs to the world of GTA III.