Question

How does an app with TestFlight send its crash reports? Is there some immediate exception handler which sends the report? Or will the next start of the app trigger a scan through the crash logs and send pending ones?
Will also kills by the OS due to too much mem usage be sent as crash reports?

Answer 1

From the documentation:

An uncaught exception means that your application is in an unknown
state and there is not much that you can do but try and exit
gracefully. Our SDK does its best to get the data we collect in this
situation to you while it is crashing, but it is designed in such a
way that the important act of saving the data occurs in as safe way a
way as possible before trying to send anything. If you do use uncaught
exception or signal handlers install your handlers before calling
takeOff. Our SDK will then call your handler while ours is running

So it is sent immediately.

I would think that memory-triggered crashes would use the same method, but you never know if it will be able to complete.