1. There is no great generic answer. Some carriers take this more seriously than others. Basic rule is that "Fasten seat belts" actuall does mean "fasten seat belts".

2. Emergency lav visits may be necessary, but opening the OH should not occur while the SB sign is lit. Stuff in the OH shifts, people jackhammer grand pianos into OHs and the like. All it takes is an open OH and a bump or swerve and you've got some poor slob crushed.