I knew most of them and disagree on some of the answers. For example, a stop sign has two sides, front and back. # 11 there is no specific direction though the argument rages on. If I have a little time I will try to find some references. 16 may be true for most fans but not necessarily all. 20. some cars have four.
Don't believe everything you read on the internet. Just because everybody knows something doesn't make it true.
BTW. does anyone know WHY the bar on a no smoking sign goes from top right to bottom left?