Hello Kingkong88888,
Welcome to the community!
@kingkong88888 wrote:
Hi, I have a new device from China, It should work with 2G gsm 850/900/1800/1900 3G WCDMA 850/2100. ..
That phone has both of the compatible bands/frequencies for 2G. With regards to '3G', that phone has one of the compatible bands/frequencies, band 5 or 850MHz. You can verify the compatible bands/frequencies here. Since the phone only has one of the compatible '3G' bands/frequencies, coverage will depend on its availability on your surrounding cellular towers. You can get an idea of your surrounding towers here.
You do not necessarily have to add the IMEI to your account for your phone to work on the network. Once you insert your SIM, the phone will register the SIM and its IMEI on the network. That said, certain features, such as voLTE and Wifi-calling, currently require the IMEIs of those devices to be in Fido's inventory database (see here). Unfortunately, if you're bringing in an unlocked device, it won't be in Fido's inventory database.
You should also note that they have begun to reduce the 2G cell counts with the view that Rogers will possibly decommission the 2G network in 2018. While there has not been any confirmation as to a firm timeline for the sunset, it will likely happen in the near future (see here).
**edit** You might need to verify your phone has the proper APN settings for the Fido network. You can verify those settings here.**
Hope this helps 
Cheers
