Firmware flash

[Iampita]

Is it possible to flash the firmware of the American version (SM-S918U) on my Japanese device (SCG20) using the Odin tool? 

[NotAdmin]

Best to flash firmwares built for your exact model as there might be hardware differences which can cause instability. Plus the device will probably be stuck in a bootloop

[Iampita]

The SCG20 version is long delayed to receive updates.

[Jacques88]

While it is technically possible to use Odin to attempt to flash the firmware, the risk of permanently damaging your SCG20 is extremely high due to the potential for hardware and chipset differences. The model number (SCG20) is a clear indication of a specific, carrier-locked Japanese device. It is not designed to run US firmware. It is strongly recommended to use only the official firmware for the SCG20 model.

[Jacques88]

If you aren't able to change your Japannese Region CSC to a USA CSC then no, Samsung always ships Snapdragon to the US so make sure you have a snapdragon SoC if those 2 aren't the same then no.

[Iampita]

Is snapdragon 8 Gen 2

[Jacques88]

If your phone is carrier locked it which it seems it is when looking up your model it makes things even more riskier - the network carriers are responsible for your devices roll out of Firmware updates.

[TeeA]

Unfortunately it's highly not recommended especially since it's 2 different model types and since your phone is region locked, you'd be bricking your phone if you do.