I have had a multifolio app available for some time on the Google Play store and Itunes store. It was made with an older version of the DPS tools - and has yet not been updated.
The app won't run on Android 4 – if I recreate binary and update the App (using the lastest tools) will it be Android 4 compatible?
Also, once the multifolio app has been approved by the Apple Store and 'takes over' the older version - will I be required to re-make and update the folios with the latest tools for them to display correctly?
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.