Whether it's jumping upwards or not, it struck upwards - simple. They're capable of striking in an upwards direction if they want to.
How often they lunge? That depends entirely on the cobra. You cannot tarnish them all with the same brush. There are plenty of cobras that will lunge straight off, forget about on an individual basis, it changes day by day!
I like how you nonchalantly say you "pat a cobra on the head"..sounds like a troll. Have any proof? Not that it's something to be proud of.
All venomous snakes have the ability to deliver a dry bite. Whether or not they do 0%, 50%, or 100% of the time, cannot be tested in a reliable manner.