Flashing iphone 3gs of 06.15.00 baseband

[tamilselvanjb]

help me to flash a iphone 3gs 06.15.00 baseband and fresh install latest iOS likely 4.3.4 or 4.3.3 or 4.3.5 and jailbreak and unlock it.
FYI
my iphone has 4.1 3gs 06.15.00 baseband and currently working with jail broken custom carrier unlocked.