You don't need Internet to access content after downloading the app. RRB Hindi is one of the best app for preparation in the market right now of upcoming RRB exam.
A free .apk file of RRB Hindi Preparation Offline 1.4 can be downloaded from Droid Informer and you can take a look at users' reviews on this site. Prepare 5 MB of free space on your device for this app installer and take into account that it runs on Android 4.1 and above. The app has been checked for viruses and it has been found totally secure. This application was originally developed by Quhasa GK IAS SSC IBPS RRB PCS Group Exams Offline and it is related to the Educational category.