iOS development with Whited00r 7 I am an iOS developer, and have an old 3G device. If I setup whited00r 7, can I use that device for development as I can use a device with iOS 7? (Register provisioning profile for that device and install ipa on it?) Are there any restrictions?
No. whited00r uses a heavily customized version of iOS 3.1.3 and 4.2.1.  They've tweaked the OS to look like iOS 7 and provide similar functionality.  They cannot backport Apple's proprietary and copyrighted iOS 7 APIs to older devices.

Additionally, the latest version of Xcode requires ARMv7 devices, which does not include any of the devices supported by whited00r.

You must have a device that can actually run iOS 7 if you want to develop apps on the device.