Asterisk is self documenting.
At the CLI, "manager show commands" will tell you all the possible AMI actions, "manager show command <command>" will give details for a particular command. The easiest way of working out what events are possible is to run the system and log the events.
There is a lot of documentation at http://www.asteriskdocs.org/
Don't assume that just because you want to do something, that it is commonly done or that Asterisk makes it easy.
What might be best for you is to set an identifier as a variable, on the Originate, then set that variable to itself in the dialplan. That will give you a newstate event that should uniquely identify the ;2 side of the local channel.