Scott Faisal

Load your project
From the menu, select Project > Edit Project Settings…
Under Architecture > Base SDK, choose one of the available device options: iPhone 3.2 or iPhone 4.0. If you are iPhone-only, 4.0 is the way to go.
Close that window.
From the menu, select Project > Edit Active Target “YourTarget”
Under Architecture > Base SDK, choose one of the available device or simulator options: iPhone 3.2 or iPhone 4.0.
If you want to target previous iOS versions, then in that same window, under Deployment > iPhone OS Deployment Target, select the lowest version you want to support. Note that support for 2.x versions through the app store is deprecated. See the “Readiness Checklist” quote above.

To uninstall developer tools/Xcode type in the following command in the terminal

sudo /Developer/Library/uninstall-devtools –mode=all

But beware, this completely removes Xcode and once it is gone, it’s gone. Of-course you can always reinstall it. So be sure of what you are doing.