The tethering function work but I got a problem that I can't use check in in Facebook and cannot use GPS navigation in Google map at 4.21
The framework hack in the OP is for 4.2. If you installed the 4.21 OTA, it would have aborted since framework was modified. If you reverted, flashed the OTA update and applied the modified framework in the OP on top of that, you probably broke a lot of stuff since the framework was modified in the 4.21 update.
You shouldn't mix and match mods/kernels/etc. across different versions of the OS.