I handle it by locking their account on my interface (not doing anymore requests). I email them once from my site asking them to reconnect their account which frees the lock (they can’t reconnect without unlocking on Twitter).
In case they unlock on Twitter but don’t reconnect on my interface, I use the friendships lookup endpoint once a day with their token just to test to see if it goes through. If it goes through, they clearly unlocked their account, if it doesn’t then they’re still locked.
To answer your questions:
- Use one of GET endpoints, I personally use friendships/lookup, with their token.
- They need to manually unlock their account.
- I think the only one I’ve come across is the verify_credentials endpoint.
- For POST endpoints I’m pretty sure you’ll trigger flags. For GET endpoints, I’m not sure but I think you’d be fine.