If your file becomes corrupt and you are unable to load, remember what you editted and put back the original vaues. Your game should load fine if you put back the original values. My way of hacking has to be that you are in the loading screen and the game ask you to load this file. This by-passes the checksum the game does every start up.
For those who are still having trouble, I have another method of editing the save file. It's somewhat like l33newhouse's and xTopWarmachinex's methods, but it should work on any iDevice, jailbroken or not (it works on my iPod Touch 5th Gen, latest iOS version, jailed). However you'll need your PC with you, with iFunBox and a hex editor installed (for me, it's XVI32 and my method will use this editor). My method below will only emphasize the editing of Inventory items. Here are the steps in full:
1) Connect your iDevice to your PC via USB.
2) Launch FinalFantasy4.
3) Select "Load Game". You should have a persistent save data in any one of the slots.
4) Select the slot with save data that you want to modify. In my example, I'll use Slot 1. You should see a dialogue box asking you if you want to load the save data. DO NOT go past that box.
5) Right at the end of the previous step, suspend your iDevice or leave it as it currently is. Go to your PC and run iFunBox if you've not done so. Navigate to your iDevice using the iFunBox Classic tab. From your iDevice, go to "User Applications", then "FinalFantasy4", then Documents. Look for a file named "save.bin".
6) Drag "save.bin" to your PC and create a backup of it as well.
7) Run XVI32 (or your preferred hex editor) and open "save.bin" with it. You can do this easily by dragging-and-dropping your save file onto the window.
8) In XVI32, make sure the first byte is selected (the top left box besides address 0 is selected) hit Ctrl-F (Find). Select the "Text string" radio button and make sure "Case sensitive" is checked. Enter "PRTY" (without quotes) in the empty field and hit "OK".
9) If you saved at Slot 1, you can proceed to edit the values. The first item in your inventory is stored 4 bytes away from "PRTY". If you used multiple save slots, count the number of slots you have used, up to the slot that you're editing. For example, if you have save data in Slot 2 and Slot 3, and you're editing Slot 3. You have used 2 slots. In XVI32, assuming you've already used "Find" in Step 8, hit F3 (Find next) one less the number of slots you have used. In this case, it's one more time.
10) To edit any value, use the left pane, select the value with your cursor, and input your desired 2 digits. If you have made a mistake, DO NOT use backspace. You'll remove a byte from the file and will potentially corrupt it. Instead, try to replace the value with the above-mentioned technique. If you're unsure, start over with your backup save.
(You can refer to l33newhouse's and xTopWarmachinex's methods for item values and what the data represents)
(If you've not made a backup, this is your last chance to do so!)
11) Once you're done editing, hit Ctrl-S (save).
12) Drag your newly edited "save.bin" back to iFunBox (you should still be at Documents in FinalFantasy4). The file will be replaced without warning.
13) Go back to your iDevice and select "Yes" in the dialogue box to load your game. If your inventory has been changed, then you've successfully edited your save file!
14) Perform a normal save at the earliest possible time to make your edited inventory stick. Based on the previous posts, I advise against performing a Quicksave.
Many thanks to xTopWarmachineX for his Guidance in editing the hex file. It works great on a jailbroken 3G itouch with 5.0.1 OS. Further thanks for providing the item hex codes :D
I realized that only iFunbox works with your method. I was using Transmit before to SSH and drag the files.
Thanks for your help
So it's definitely confirmed that this iOS version only provides 1 Limit Break augment in 3 playthroughs? And the only real workaround is hacking your save file to give yourself a second Limit Break?
Has anyone calculated out a way to max the Final Five's stats to 99 with just ????'s Love and 1 Limit Break? I'd just rather avoid all the hex-editing.