There's an emergency and you or someone else needs help. Don't just yell, "help". Instead be specific like "you with the bad outfit, call an ambulance". You'll avoid the "bystander effect" where if people aren't called out specifically they'll freeze and not know what to do.
Most people don't have one and not all fire extinguishers are suitable for all fires. This is actually the best way because you cut off the oxygen and don't make a mess.
Not where I live.
#9 and you better do it under 10 nanoseconds