If you don't have rooted android phone, then you can try https://play.google.com/store/apps/details?id=com.suttittech.dfr
*** How To Use ***
1. You have option to install any one of two different devanagari fonts.
2. Click on 'Install 1' or 'Install 2' button.
3. Phone will be rebooted automatically, to apply changes.
4. Check if devanagari messages can be seen properly.
5. If you want to use another devanagari font, then click on alternate button.
6. Phone will be rebooted again automatically, to apply changes.
7. Hopefully, devanagari font will be installed in your device.