The type specific competency requirement for using crew seats was ditched some years ago.
Now you just need to be AE current cockpit crew, cabin crew or safety training school instructor.
It can be hard to say generally, how many crew seats are available. There are a lot of variables with crew numbers on any specific regional flight, depending on issues such as extra crew for duty free sales etc. There is a lot of Cabin Crew training and re-training going on as well, so often crew on Familiarization flights etc.