I have never downloaded a digital copy of a movie before, so I had assumed that you would only go to the website listed on the movie insert and download it from there. Apparently, there's a few extra steps to get it on an iPhone/iPad, but it looks like it can be done. I can't guarantee that it will work, though, since I have never experienced it. Check out this website for info: https://www.disneystudioshelp.com/detail_Oz_iTunesHD__DIGITALCOPYHELP.html.
It is for getting Disney movies, but I think it would work the same for any other website you would go to in order to redeem (this one specifically says to go to FoxRedeem.com).
I assume so. You access the FoxRedeem website from any web-accessing device, and it should be good to go. I have never downloaded a digital movie before, but I think it just goes on to whatever hard drive saving system you have for that device or into an account somewhere and you can then use it on a different device than the one you downloaded it to.