A link to the application of which you are speaking would be helpful. As for playing games on that machine, your specs are a bit low to play any modern games.
Probably not, as that iBook is very old and can't can modern games, unless you want to play games, that have similar requirements to the specifications of that iBook.
Windows is programmed for X86 (Intel), thus no PPC version exists and no PPC games for Windows are available.
The uses of Windows on Mac: running Windows on Mac for Windows only applications, as most games and some specific software titles I'm too lazy to list here.
An Intel Mac is better suited for running Windows though, as running Windows on a PPC Mac is like watching flowers grow.