Yes C or C++, although the programing environment is unlike the Mac and Xcode because of the interface. On Mac it is much easier, but still takes skill.
if you mean make an app, buy a mac, get Xcode, learn how to program objective C (cocoa touch) get a dev lisence, release it on the app store :)
Xcode is made by apple its a developing app for programmers so the answer is yes
You can't install XCode or its SDK on the windows. All you can is create a virtual machine, install Mac OS X there and then install XCode and SDK.
the genious sidebar on itunes is good for that
Desktop
From Xcode, having safely saved all your source files, you Build an application by clicking the Build button in your Xcode toolbar or pressing the Command and B keys if you do not have a Build button.
you need a mac, you need xcode and interface builder, etc. and you need to know how to use code. if you don't, you can buy books to teach you how to program
XCode for will work on any standard MacBook Pro no upgrading is required. If the Mac is running Lion (OS X 10.7) it will need XCode 4.1.
shipped with OS X
No you can not get xcode on any windows operating system i heard (even thought this may be in correct) that only MAC OS X users can get this.
Yes! Right-click your desktop, and then select "Gadgets". This brings up the sidebar and the sidebar options.