Can Iphone 4 be used with sprint unlocked?

Yes the iphone 4 currently is being sold on Verizon and AT&T currently but should be expected to be on Sprint shortly. Sadly though only the iphone 4 runs on CDMA networks as well as GSM. If you are thinking you can unlock an iphone for Sprint or Verizon that's under the fourth generation like the 1g, 2g, 3g and 3gs, it wont work.