Samsung Galaxy J3 Pop
The latest firmware for Samsung Galaxy J3 Pop (SM-J327AZ) is J327AZTUS5ASE1, released on May 1, 2019 for 1 region (CSC). Every official firmware build for SM-J327AZ, 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/J327AZTUS5ASE1
The newest build, J327AZTUS5ASE1, was released on May 1, 2019. No new build has appeared for 91 months, so regular updates for this model have most likely ended.
Specifications of SM-J327, a regional variant of the same device. Chipset and SIM lines are left out: they can differ by region.

SM-J327VPP

SM-J320VPP

SM-J326AZ

SM-J337A

SM-J330N
The latest build for SM-J327AZ, J327AZTUS5ASE1, was released on May 1, 2019 (7 years ago).
SM-J327AZ has had no new firmware for 91 months, so regular updates have most likely ended.
Yes, all firmware files for SM-J327AZ are 100% official, original, and obtained directly from Samsung servers.
To flash SM-J327AZ, 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-J327AZ.