Yeah, they do that because it's a tradition passed on by the British. They will ask a doctor to check for 0 pulse before pulling the remains down.
Nop, its not like that. Human life cannot be taken in 2-3 sec by hanging. There are 2 scenarios what happens during hanging when it comes to gallows. 99% of it done by professionals
will lead to the neck breaks and severs the spine, blood pressure drops down to nothing in about a second, and the subject loses consciousness but death itself will take 10-20 mins to arrive.