It's ridiculous that you cannot open the previous version of a Pages file in the current version of Pages! What an absolute joke.

That would violate the Keynote license agreement. So, we're back to needing Apple to help out here.

edit: from Section 2A, Permitted License Uses and Restrictions... i) to download, install, use and run for personal, non-commercial use, one (1) copy of the Apple Software directly on each Apple-branded computer running OS X (“Mac Computer”) that you own or control; and (ii) if you are a commercial enterprise or educational institution, to download, install, use and run one (1) copy of the Apple Software for use either: (a) by a single individual on each of the Mac Computer(s) that you own or control, or (b) by multiple individuals on a single shared Mac Computer that you own or control. For example, a single employee may use the Apple Software on both the employee’s desktop Mac Computer and laptop Mac Computer, or multiple students may serially use the Apple Software on a single Mac Computer located at a resource center or library.

Except, right now, it doesn't. If that was their primary design goal, than it has not been achieved, because their web version still lacks features that are front and center on the desktop. So, you can't use that as an excuse.