I've already answered that in the thread you've linked above, and since then no new discoveries came up.

Win 98 is not able to properly run DirectX9 applications. You need at least Win98 SE.

Win98 SE can theoretically run DirectX 9 apps. This will work when you run a very small 2D app, like the pong demo. Larger apps will soon run into memory limits of such an old system, and thus we don't officially support 98 SE. 90% of all Gamestudio applications will not run on an average 98 SE system even if it's properly configured.