You can "restore purchases" for IAP unlock content if you delete and redownload. The IAP unlock is tied to your App Store / iTunes account so any iDevice you log into with that account can download and restore purchases. This is standard for all non-consumable IAP content on App Store.
Here's another situation, it's been backed up to my iTunes and I've deleted it from My phone. For whatever reason square pulls the game from the App Store. Maybe it's 2016 or something. Am I out of luck getting to play the game? I've gotten comfortable with the idea that games get pulled from the store and I need to back them up... I just can't get comfortable with ever buying something through IAP.
I'm still debating of getting all the chapters... next week FF iV is coming out... what to do...what to do....
I can't give you a definitive answer but understand sometimes when apps are pulled they remain avaliable for download through "purchased" games in account history for those who previously purchased. That makes me suspect you could restore purchases even if pulled. Otherwise I imagine it depends on if some purchase information was saved locally on the device or backed up app. If you want to definitively own any game forever no matter what then that might not be realistic to expect but if you want a game to enjoy for the time being then here you are. With Square investing more and more in App Store products I doubt they will disappear or pull apps anytime soon.
This game is pretty amazing... I'm still on chapter 2 and im 16 hours in already. The story isn't as good as FF4, but its still better than FF1-3. Def worth the purchase... its CONSOLE quality and a FF game for retro gamers and those who loved the FF series before FF went downhill starting with FF7. I'm still waiting on FF5 and FF6 to be ported to the iOS FF6 was the best! BTW just from someone who grew up playing RPGs on the best consoles (Nintendo + Super Nintendo). If you were to only purchase one final fantasy game on the appstore, its Final Fantasy Dimensions. In fact, I would bypass FF1-3 completely.
Somehow FFIII has gotten stuck in my backlog but having grown up playing NES FFI I started FFD first because the "retro" 2D gameplay looked more appealing. From feedback it sounds like a lot of people enjoy FFIII so I imagine it's more accessible, but I'm really enjoying FFD.
I started with Dragon Warrior then FFI my Favorate is still FFIII on the Snes that set the standard I never played the FFIII that is aviable on ios I hated when they moved away from the classic look of the characters FFVII is a close second
It sounds like Final Fantasy Dimensions will be right up your alley. That was one of the reasons I've backlogged FFIII [iOS], because the 3D "remake" bothered me a little, and the day I first played FFVI[Japan]/FFIII[SNES] changed my life. It sounds like we have similar tastes in RPGs so you'll like find Final Fantasy Dimensions as satisfying as I have so far.