Model or internal factory #s I am guessing (possibly different from different generations). Not serial #s as I’ve got 3 transmitters that have same as yours).
I’ve flown up to five. Not sure how many more would work, I think total bandwith available will be restricting factor.
I haven’t specifically seen this behavior, but I would assume because battery level is critically low
No, can only have one channel at a time. But you can have one transmitter to several skyvipers! Handy if you have a swarm and things go wrong!