If I download a resource and the resource is later updated, will the updated resource be automatically downloaded again?
No - it's purely manual.
On the iPad version of the app you get notified - in the home page - that there are "N" resources to upgrade and you then can choose whether you download all of them or individual ones.
I would expect the Android app would get this some day.
Graham
Now I know what Mac users must have felt like[:(]