For the people who can't login their Houkai 3rd via Facebook:
1st.) If you have a mihoyo account bound then use that.(if you did not bound your account through mihoyo then move to step 2.
2nd.)Go to sdcard -> Android -> data and change the houkai files or add 1 go to Android -> obb and change the houkai files or add 1.
3rd.) Uninstall the modded version and keep the apk.
4th.)Open Google play and install the houkai 3rd
5th.) After installing, repeat step 2 and change them back to the original.
6th.)Login via Facebook, if not working and it crashes(crashing,stoped) then install Facebook and restart your phone.
7th.)Login through Facebook and after logging in, go to you profile and go to your account. After that, click that mihoyo to register it at your account.(input details ofcourse)
8th.)Before uninstalling the app go back to step 2 and after that you can now install the modded app. Thus, you can now login via mihoyo and Facebook. (Step 2 again and revert it to the original file name)
~hope it helps~