Nope when you make changes in your site ,there is record is kept for each change you do ,updation of course or unit .
Then when user opens up the app there is an api call made to server to check which things(units,courses) are updates on site . App code checks for each things and remove the things from offline storage .System then check for it in local data when it does not find it then api call is made to fetch that item again .
this is how it works .
For instructor data ,I guess we are not tracking that as of now but for course and units ,yes we,re tracking but for that user need to close the app and open it again .