My Iphone Is Not Updating

Write down the Error Code so you can look up the cause and solution of this Error.

See Here for Error 1604...

http://support.apple.com/kb/TS3694

1. Connect the device to iTunes, confirm that the device is in Recovery Mode. If it's not in Recovery Mode, put it into Recovery Mode.
2. Restore and wait for error 1604.
3. When prompted, click OK.
4. Close and reopen iTunes while iPhone remains connected.
5. iPhone should now be recognized in Recovery Mode again.
6. Try to restore again.

That Error Message suggests the Device has been hacked...

http://support.apple.com/kb/TS3694

Why Jailbreak is Not Supported

http://support.apple.com/kb/HT3743

Error 1015 is most commonly a downgrade Error. If you were downgrading your iPhone then that is why you got the Error 1015. But you were not downgrading your firmware, you were trying to Restore with the current Firmware 4.3.5, so why the Downgrade Error. Most likely your iPhone has the iPAD Baseband (Modem Firmware) which is at a higher #, than that in Firmware 4.3.5, so a downgrade attempt of the Baseband was made by iTunes. Apple will not allow that.

If your iPhone has the iPAD Baseband you will need to search the Web for Custom Firmware.