Hi,
Good question indeed.
Action 4 will be executed when Action has been called, regardless of it's finished state.
I don't get your second question, but I think the answer is that yes, it will occur in the same frame and code stack of execution.
No way to put a breakpoint on action, it's per state. So move Action 4 into a new state following the current state, then you can breakpoint on action 4, and the process will be identical in terms of execution flow.
NOW, a state has an option to be "sequential" which means each action will wait for the previous action to have finished, and so in that case, Action 4 would only be executed after Action 3 has called finished.
Bye,
Jean