
Samsung Galaxy Core Prime
The latest firmware for Samsung Galaxy Core Prime (SM-G360R6) is G360R6WWS1AQD2 with Android 5.1.1, released on April 4, 2017 for 1 region (CSC). Every official firmware build for SM-G360R6, newest first: one row per build with all regions (CSC) that received it.
Each firmware build has its own page at https://samfirm.shop/build/{PDA}, where {PDA} is the build number from the list above. Example: https://samfirm.shop/build/G360R6WWS1AQD2
Specifications of SM-G360F, a regional variant of the same device. Chipset and SIM lines are left out: they can differ by region.

SM-G360AZ

SM-G3509

SM-G3589W

SM-G357M

SM-G3568V
You can find the firmware on the model: SM-G360R6 page.
Yes, all firmware files for SM-G360R6 are 100% official, original, and obtained directly from Samsung servers.
To flash SM-G360R6, you need to download the appropriate firmware, put your device into Download Mode, and use the Odin tool to load the BL, AP, CP, and CSC files.
Downgrading is only possible if the bootloader version (binary bit) of the old firmware matches the current one. Always check the binary version before flashing SM-G360R6.