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You have a number of questions here.
The iOS app is not actually native Sage. What the apps (also the Android one) do is to communicate with a server API that computes individual code fragments one at a time. (Which is still powerful, if you have a long enough fragment.)
Dependencies are at the components page of the Sage website.
R code can be run in several ways, documented in various places; here's a question on this site which mentions some.  I don't think that the %r syntax works in iOS yet (?) but the r.kruskal_wallis() method should work okay.  A lot of people use Sage and R together effectively (including myself) to use the best of each.
Haskell does not interface with Sage.
I should point out that a lot of this would have been pretty easy to find with a generic web search, but hopefully this will help not just yourself but others looking for it as well.
 Copyright Sage, 2010. Some rights reserved under creative commons license. Content on this site is licensed under a Creative Commons Attribution Share Alike 3.0 license.
 
                
                Copyright Sage, 2010. Some rights reserved under creative commons license. Content on this site is licensed under a Creative Commons Attribution Share Alike 3.0 license.