Is the iPhone cellular data limit enforced in 3rd party Apps?

Question

I know nothing about iPhone development, but I am drafting a proposal for other people to do the work of creating an App that interfaces with existing systems and data.

Answer 1

No. The 20MB limit is one imposed by the App Store itself. The only restrictions seen in third-party apps are ones that the cellular provider wishes to enforce (which typically just means bandwidth caps or overage fees if you go over a download cap). That said, it may be useful to support HTTP Range anyway, in case the download is interrupted and you wish to resume it.