Majority of that stuff is old wise tales, even ultrasounds can be wrong unless you get a 3D ultrasound. Some of it is fun to do though. I did the baking soda test (if it fizzes = boy, if it doesn't fizz = girl) and the Chinese gender chart and both said I was having a boy, and indeed I had a boy.
Chinese gender calendar has worked with my last 2 children. We will see with this one ...
Nope. Besides birth, there is no 100%. Ultrasounds can be read wrong too.
All My "Wives Tale Symptoms" Were Signs Of A Girl But I'm Having A Boy! The Only Thing That Worked For Me And Was Accurate Was The Chinese Gender Calendar.