for other region means? if you want to download firmware of Russian model of A20s in india then it's not possible because kernel version and serial number will not matched. ..it's depends on kernel compatibility ..according to which software has to be made differently for same device different region wise
may be you can't install that serial number bhi compatible hona chahiye...nehi hoga ....that device is AT and T carrier locked you can't install same firmware here in india with same model but different kernel version of your device...as an example this is my device kernel version 👉 ....now specific software is there to match with this only
