I'll be completely honest, I haven't had too many problems with my phone which doesn't have a VPN on it. I forwarded all my Gmail to a Hotmail and switched Google to Bing. Flyertalk works fine.
Messenger, WhatsApp, and Instagram don't work which is annoying. I'm using all the local apps instead of the foreign equivalents (e.g. Gaode 高德 instead of Google Maps), and the Apple built-in equivalents work too.

Public wifi in airports either requires you to receive a SMS with local number OR pick up a paper number from a kiosk. Once you get the SMS it logs in instantly. I have not been able to locate a kiosk by casually looking but I assume they're there? Asking the lounge person for the code also works. I haven't used public wifi otherwise because I have enough data.