The -2B19 designation is used for both 100 and 200 models (and, come to think of it, the 440 model). As you say, the 100 models use the 3A1 engine and the 200 the 3B1 engine.
The fire push does not give you an instantaneous shutdown. At the factory, we shut them down from idle using the fire push and IIRC they were allowed up to 30 seconds.