1. Whether it will work outside the US depends on where. If they're using Band 32, no, otherwise, the US version has some bands that the global version doesn't.
2. If you use the military version of iShredder, not even the government could recover the shredded data - it's just not there to recover. It's as "recoverable" as if you run the phone over with a steamroller, smash the bits remaining with a 50 pound sledge hammer, then roast them for an hour at 8,000°C. Not even Superman (if he existed) could recover any data from that. System data? Yes. All your system apps are still there. But deleted files, uninstalled apps, cleared cache, deleted data? All turned into random junk. (I've played with data for a few decades. Just writing random to a hard drive 100 times makes the data unrecoverable to anyone except, maybe, an expensive lab. [Magnetic media may still retain a few magnetized molecules. but electronic storage? One random write is enough, there's nothing left behind. Doing it 10 times just randomizes it more. Doing a military wipe? That "unrandomizes" random bits - in a random manner. Without telepathy, recovering a single useful bit from that is as possible as determining your 10th descendant's name. The data just isn't there, so there's nothing to recover.) Even just running dd from a terminal app, inputting from the pseudo-device /dev/urandom, will give you unrecoverable storage, but you only want to wipe unused space, and that';s what iShredder does. (If the phone won't be checked to see if there's a ROM in it, or if you can flash a ROM, just flash a stock ROM, run iShredder, and uninstall iShredder. All that's "recoverable" is that you had iShredder installed. Once anyone sees that, they won't waste time trying to "undelete" anything - they'll know that there's nothing to undelete. Risk your family? Why do you think the president of the US is issued a government phone, then it's taken away when he leaves office? It's shredded, that's all. Then it can be used by any other government employee. (It's going to be 4 years old, so you don't want the next president to use it.) But if there were government secrets on it, even the CIA is comfortable knowing that there's nothing left on the phone.