Scammed by Amazon , M8x Taiwan Version , Need your advice ( S-Off , Firmware , Wifi ) topic

Hello , Thank you for taking time to read and help me with my questions , recently i recived my M8 from Amazon , it was stated clearly that the phone is the international version , but after going through the infromation in the Hboot , it turned out to be a Taiwan version , with these information :

modelid: 0P6B11000
cidnum: HTC__621

I managed to get Hboot unlocked , flash custom recovery and HDR Rom , all is going good , but after going through the threads , i noticed that my Firmware is 4.16.709.9 , as it says OS_info : 4.16.709.9 in Hboot screen , and the ROM firmware is 4.16.401.10 , as most of the roms are.

So ,

1- do i have to flash 4.16.401.10 firmware to match the ROMS ?

2- Can i do that with out bricking my phone ?

3- if yes , then i have to S-Off right ? Sunshine says that it is not compatible with my phone , is that because i am on a custom rom ?

4- What will i gain from switching the firmware to 4.16.401.10 ?

5- THE MOST IMPORTANT QUESTION : Before i do any thing with my phone ( when it was fully stock ) , it had 5.0.1 Android , and i noticed a problem with few apps not being aible to connect to internet via Wifi some times , but they works perfectly if i use a VPN app , or if i use my 3G connection , i thought if i flash another rom it will be fixed , but no , it was not fixed , will flashing the 4.16.401.10 firmware solve this ? or is it a lollipop android problem ?

Thank you so much for your time ! i really appreciate your help