Yeah you need an iPad. There is an iPhone version that went free for a day a long time ago...finally the iPad version went free, yay! iPhone version is only a dollar IIRC if you really want to play it. The game is awesome on the iPad
No. You just need an iTunes account and your Mac/PC. Download for free NOW and transfer/download again on your iPad when you buy the device LATER (highly recommended). Works highly accurate, tested often. For actually playing the game you need an iPad naturally.
I tried the Lite version and liked it but I was a little disappointed to discover there were no random weapon/armour drops. It was all just instant gain items otherwise I'd probably purchase it.