Kinda confused about this OS. How many versions were released? What's the latest one? Can you run Win98 apps on the latest one? How much does it cost and where can I get it?

As best as I can recall both IBM and Microsoft released 16 bit versions, 1.0, 1.1, 1.2, 1.3. Afterwards IBM released 32 bit versions 2.0, 2.1 and starting with version 3 they called it Warp followed by Warp connect and later Warp 4. Also included are a couple of versions of Warp server, but I don't know too much about them. Warp 3 came in two different flavors. One without DOS/Windows 3.1 support (red) and one with DOS/Windows 3.1 support (blue). Basically the current version of Warp is version 4. Currently there is also an upgraded version of Warp 4 known as E-Comstation which is Warp 4 with all the fixes. Some have refered to this as Warp 4.5 Cheapest way to go would be to purchase Warp 4 and also get all the fixes on CD.

Rick mate, buddy, Why are they called win98 apps?
I mean for gods sake, some people. Can I run playstation games on a nintendo 64?
(It can though run (16bit)win3.1 apps)

OS/2 can run SOME 32-bit Windows applications (which would be a subset of "Win98 apps") through a built-in emulator called Odin. There's also a plugin, similar to WINE for Linux, that allows OS/2 to run some X-based Unix applications.

If you're interested in Odin, have a look at odin.netlabs.org (though their server seems to be down at the moment).
Actually, I'm using Odin right now: I found this nifty little win32 program called eDexter which acts like a mini http-server. I've got about 500 adservers in my hosts file, all redirected to localhost. Once a site tries to contact one of these adservers, the request is redirected to my machine (eDexter server a 1x1 transparent gif) - thus I see basically no banner ads. Nifty.