I live in the Philippines. And I saw that Vietnam had their J2 Prime upgraded to Nougat since 2017. I tried mine and it says that the latest software is already installed. Can I change my phone's country so that I can upgrade it?
The upgrade comes from your service provider, not where the phone is located. You may be able to flash a newer ROM to it manually but you risk bricking your phone and it may no longer work with your service. IMHO, not worth it. You have a working phone, you start messing with it, you may not.