
Samsung Galaxy Note3 Neo
The latest firmware for Samsung Galaxy Note3 Neo (SM-N750) is N750XXUDPA3 with Android 5.1.1 (KitKat), released on January 26, 2016 for 4 regions (CSC). Every official firmware build for SM-N750, newest first: one row per build with all regions (CSC) that received it.
SM-N750 started on Android 4 and has received 1 major Android upgrade; it now runs Android 5.1.1 (KitKat). The newest build, N750XXUDPA3, was released on January 26, 2016. No new build has appeared for 130 months, so regular updates for this model have most likely ended.
Specifications of SM-N7505, a regional variant of the same device. Chipset and SIM lines are left out: they can differ by region.
Box codes of SM-N750 for different colors and markets. Firmware is chosen by the model code SM-N750 and your region (CSC), not by the SKU.

SM-N920AZW

SM-N920VZW

SM-N950UZK

SM-N920AZK

SM-N950X

SM-N930V

SM-N9300

SM-N930S
The newest firmware for SM-N750 runs Android 5.1.1 (KitKat): build N750XXUDPA3, released on January 26, 2016.
The latest build for SM-N750, N750XXUDPA3, was released on January 26, 2016 (10 years ago).
SM-N750 has had no new firmware for 130 months, so regular updates have most likely ended.
Yes, all firmware files for SM-N750 are 100% official, original, and obtained directly from Samsung servers.
To flash SM-N750, 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-N750.