I mistakenly uninstalled my Download Manager 4.4.4 in my Samsung Galaxy Grand prime G530H. A system application. I tried replacing it with a Download Manager 2.3.5. I did that by using a file explorer to place the 2.3.5 in the system folder. Then I rebooted the phone. It didn't work. The phone doesn't recognize the 2.3.5. Looking through the file explorer I can see the Download Manager 2.3.5 is still in the system/app folder and I tried deleting it but it won't delete. I need help on how to get the original Download Manager 4.4.4.
MANI's answer regarding resetting the device, this may assist you, but as far as I am aware a reset does not touch where the applications are actually stored.
What is a ROM?
Read Only Memory. Essentially just a new firmware/software for your Android Phone. For a more detailed explanation and information on a ROM look on this website. If unsure if you should do this process, read on How To Geek about the "Top 5 Reasons to install a Custom ROM"
Process for your Phone
Here is an example of how to install a custom ROM on your phone (including Drivers, links to ROM etc.)
Here is the Xda Forum for your phone. Covers troubleshooting, ROMS etc. I would suggest you look here also.
Refer to this question on SE that provides a detailed answer (thanks @Izzy)
Hope this helps you. Undoubtedly a Factory Reset could assist, but I am not 100%. The steps for a Factory Reset on your device are located here.