iReb is what you need to to get yourself out of iTunes error 1600, 1602, 1603, 1604, 1015 when doing a firmware restoration your device is placed into pwned state.
iReb r5 does not bring any major update let alone support the A5 device, as of course there are not bootrom exploits for those devices available right now.
However improvements are placed in this release, these are official logs of the tool:
- Much smaller file size (390kb).
- Fixed USB 3.0 issues.
- iREB's speed for the iPhone 2G/iPhone 3G/iPod Touch 1G has increased significantly!
- Fixed rare DFU detection issues.
- Updated limera1n/steaks4uce payload to not hook "cmd_go" on 4.x images (nothing severe, but useless here).