Can I upgrade my galaxy s5 model SM-G900I to the firmware of another country/region but of same model no?
Yes! You can. But, for doing it you need to change your phone's CSC code.
Samsung was using an special CSC file included in Android firmware which are specifically built and designates to each country or mobile network providers.
Changing the CSC code to the corresponding country's CSC of which you want to flash the firmware will work for you!