From 8.0 to 8.1 is a free upgrade from Apple's Older Software Downloads page. Same from 8.5 to 8.6. Those are really the only relevant point releases of MacOS 8.
But to go from 8.0/8.1 to 8.5, you have to find a disk of 8.5. It's not a free or downloadable upgrade.
Both 8.1 and 8.6 are nice and stable. The others ... yeah, not so much. 8.1 is a bit easier on memory requirements too, but 8.6 is more OS 9-like.
And we don't discuss "sharing" copyrighted material here.
But to go from 8.0/8.1 to 8.5, you have to find a disk of 8.5. It's not a free or downloadable upgrade.
Both 8.1 and 8.6 are nice and stable. The others ... yeah, not so much. 8.1 is a bit easier on memory requirements too, but 8.6 is more OS 9-like.
And we don't discuss "sharing" copyrighted material here.