> [i] Boys and girls, men and women are very different.
People are different, splitting people up into two groups generally doesn't help anything. The vast majority of your life will be spent dealing with individuals, not groups. Don't treat individuals like any of their groups.
> (A) The cliche that boys pay attention to things and girls, to people is not fully true but significantly often is true.
I have found nothing of significance in my life due to this purported "fact". People are people. Look at the individual, not the group.
> (B) Once from a real expert I got a flat statement: "Of COURSE, women are MUCH more emotional than men. That is the cause of all the problems.". That answered a lot of questions!
Uninteresting. Maybe you are less emotional. Maybe the people you dated were more emotional. If that is a problem, seek out less emotional people to date. There are plenty. More importantly, find someone that makes you feel good, regardless of any insipid advice about "women".
> (C) A large fraction of girls and women tend to be afraid -- the list is long with some standard items and some more. One of the more important things a boy/man can do is make it really clear to the female that they are at zero risk with him.
You should do this with anyone.
> (D) Generally girls/women are exposed to some means of manipulation, and some of them get good at it -- boys/men need to watch out for that.
Men manipulate just as much as women. Again, look to the individual. Stop thinking in terms of men vs women. Find someone that isn't manipulative.
> (E) Some girls are afraid of being in love (there is a lot to understanding love, and I can't cover all of it here) but, still, are very interested in sex. For them, holding hands can be more intimate than sexual intercourse. Boys/men need to realize that.
Take the gender out of this statement and it is an interesting one.
> [ii] A surprisingly large fraction of people are in some significant ways seriously mixed up. So, watch out for that. Also have a list of common ways and watch out for those.
See, great statement, absolutely decent advice because you kept gender out of it. Although it does sound too jaded. I'd rather state it as, "people struggle with life, understand a person's struggles and make sure you can handle them before becoming too deeply involved with them, not just romantically, but platonically, too."