Got it on the iPod 4th gen.

Wanna know a duplicating cheat? Okay all you need is a block. Any kind don't matter, even iron, gold or diamond blocks work. Put it down, press home button, erase the app from the multitask bar, open the app bak up and go bak to the game. You should have the block you put down and one in your inventory. If you put 2 blocks, do the steps, you'll get 2 in your inventory, same with all even numbers.

Doesn't work sometimes, but it does most of the time for me.