This firmware iOS 4.0 will update iPhone baseband to 05.13.04. Latest release of OS comes with lots of new features like multitasking, folders, unified mailbox, new wallpapers, threading in Mail, lots of enhancements in camera and photos, deeper enterprise support, , Retina Display integration for iPhone 4 and tons of new features everywhere.” and much more.
Download Firmware From below
You could also connect your iPhone with your computer and launch iTune, then it will prompt you for updating to latest iOS 4.0.
For JailBreak Read This – Jailbreak iOS 4.0
For Unlock Read This – Unlock iPhone 4, 3G & 3GS On iOS 4.0 With UltraSn0w
You could always get support from UnlockAlliPhone.com about any Unlock & JailBreak issue of any model of iPhone including iPhone 2G,3G & 3GS and also upcoming iPhone 4. They provide Premium Members Support for life time. Means just pay one time a small fee and you will receive support(real human support – avg response time 2 hour) for all present & future version of iPhone.