
Samsung Galaxy S4 (Verizon)
The latest firmware for Samsung Galaxy S4 (Verizon) (SCH-I545) is I545VRUGOF1 with Android 5.0.1 (Lollipop), released on July 14, 2015 for 1 region (CSC). Every official firmware build for SCH-I545, 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/I545VRUGOF1
SCH-I545 started on Android 4 and has received 1 major Android upgrade; it now runs Android 5.0.1 (Lollipop). The newest build, I545VRUGOF1, was released on July 14, 2015. No new build has appeared for 137 months, so regular updates for this model have most likely ended.

SCH-R970X

SCH-L710

SCH-I939D

SCH-I545PP

SCH-I545L

SCH-I435

SCH-P709

SCH-W899
The newest firmware for SCH-I545 runs Android 5.0.1 (Lollipop): build I545VRUGOF1, released on July 14, 2015.
The latest build for SCH-I545, I545VRUGOF1, was released on July 14, 2015 (11 years ago).
SCH-I545 has had no new firmware for 137 months, so regular updates have most likely ended.
Yes, all firmware files for SCH-I545 are 100% official, original, and obtained directly from Samsung servers.
To flash SCH-I545, 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 SCH-I545.