Install legacy iOS

Question

Greetings,
I'm currently deployed, so my options for support are very limited.  In short, I'm looking for guidance on how load a previous version of iOS so I can restore a data backup, rather than losing 2 years worth of Text message history, phone settings, and app organization/setup.  Please see below for the full backstory.
My iOS device which requires assistance is a iPhone 4, CDMA (Verizon), model:  A1349.  Recently, over the last several weeks (since upgrading to iOS 7), my device has been performing poorly and apps which utilize the locations services (such as fitness run tracking apps) have failed to maintain my location (I have to now manually enter the data). 
Hoping that my issues could be resolved by a clean iOS & data restore, I decided to do so on Monday.  Fortunately, I have WiFi in my location (free & it works), which although is extremely slow, allowed me to download the iOS 7.0.2. restore '.ipsw' via iTunes.   By the time the download finished, it was literally hours after the Apple event earlier in the week, so iOS 7.0.3 had been released.  When I tried to run the restore with the version I downloaded, iTunes automatically deleted the 7.0.2. file, and began the 7.0.3. download.  Honestly, at this point, I didn't think it was a big deal, so 2 days later when the download finished, I ran a full-encrypted backup of my phone again and proceeded to restore to iOS 7.0.3.
Unexpectedly, after the iOS 7.0.3 install was completed on the device, I attempted to load my phone's data backup.  I recieved an error message from iTunes stating that the backup had become corrupted or was incompatible with my iPhone.  I restarted my computer several times, rebooted the iPhone several times, and recieved the error message each attempt.  As I said, I have quite a bit of history in the data in my phone... everything from text messages which will likely become evidence in a court case to conversations with my wife/family while I've been deployed which I'd like to keep. 
I've narrowed down the idea that it's likely because of a change in 7.0.2 -> 7.0.3 which is preventing the restore.  So, over the last 3 days, I've been trying to download iPhone3,1_7.0.2_11A501_Restore.ipsw via Apple, however I continually get a .zip, even though the link is pointing to the previous file format.  Sadly, I won't have a Mac until I get back from deployment (Win 8 PC currently), so when I started doing research on how to extract the ipsw from the .dmg file inside the .zip, I though this would be an easy matter... All attempts have failed.  I've received consistent error messages ranging from either the file is corrupt to encrypted formats aren't supported by the software I've attempted to use to extract the ipsw. All of the walk-throughs I found to extract the file showed that there was only one .dmg file inside the zips, however my attempts have always had 3 of them in it... and none will open.  Last night, I to download the file again, since I considered based on my reading that the .zip may have been corrupted somehow.  Today's download produced the same results. 
So, what I'm hoping for is a way to download the 7.0.2 software or extract the ipsw from what I have.  My goal is to restore the older version, restore the data, update the phone, backup as a 7.0.3. device, then restore it again with that version ... hopefully it will run cleanly.  There may be a simpler way, and I'll gladly hear/read any advice.... as I said, it would really hurt to lose everything. 
Thanks in advance.

Answer 1

Like it or not, there is no supported way to downgrade, as such is not supported by Apple & cannot be discussed here, per this forum's terms of use.