
Samsung Galaxy S 4 (Sprint)
The latest firmware for Samsung Galaxy S 4 (Sprint) (SPH-L720) is L720VPUGPI2 with Android 5.0.1 (Lollipop), released on September 6, 2016 for 2 regions (CSC). Every official firmware build for SPH-L720, 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/L720VPUGPI2
SPH-L720 started on Android 4 and has received 1 major Android upgrade; it now runs Android 5.0.1 (Lollipop). The newest build, L720VPUGPI2, was released on September 6, 2016. No new build has appeared for 123 months, so regular updates for this model have most likely ended.

SPH-M840

SPH-L900

SPH-L710T

SPH-L720T

SPH-L710

SPH-L600

SPH-L520
The newest firmware for SPH-L720 runs Android 5.0.1 (Lollipop): build L720VPUGPI2, released on September 6, 2016.
The latest build for SPH-L720, L720VPUGPI2, was released on September 6, 2016 (10 years ago).
SPH-L720 has had no new firmware for 123 months, so regular updates have most likely ended.
Yes, all firmware files for SPH-L720 are 100% official, original, and obtained directly from Samsung servers.
To flash SPH-L720, 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 SPH-L720.