If you see SW REV CHECK FAIL in Odin, you are trying to flash an older bootloader than what is currently on the device. Samsung prevents downgrades on the SM-R800 after binary bit U3 (released mid-2020). You can only flash the same or newer bit version.
If you encounter issues during the firmware update process or experience problems with your device, try these troubleshooting tips: Sm-r800 Firmware
Although the SM-R800 is a Bluetooth-only watch (no LTE), the CSC still matters for features like Samsung Pay, Samsung Health sync, and available watch faces. If you see SW REV CHECK FAIL in
Firmware for the SM-R800 is a proprietary software package developed by Samsung that includes: Samsung Health sync