Supported versions of Android OS are :
4.x (Ice Cream Sandwich).
Your DPS App should run fine on Android unless it is not a stock OS. You can try updating the Android app to latest Viewer and leave apple one alone if you like.
Regarding your second question : Newer versions of Viewer Apps have backward Folio Compatibility thus older folios would be visible in the new App.
Excellent. Thanks for your help!