Is it possible for extensions access the containing-app's container directory?
For iOS5-based app, i don't want to move all my old data into shared-contatiner, i wish that main-app can remain the same, and the extension just read & write the old data directly, that will be perfect!~
Your widget may never access the containing app's data directly, only if the containing app puts that data into a shared container using app groups. The documentation (including the WWDC videos) is pretty clear about this.
There's a high chance that your iOS-5-based app needs major changes anyway to work nicely on iOS 8.