Thank you for trusting JustAnswer with your important question.
There are many reasons why a man may like to hold a woman from behind.
For some men that is less emotionally threatening than being close in a face-to-face way. Other men may feel protective or want to show ownership (This is my girlfriend!) by standing behind someone or by often having a hand on their partner. These signals effective tell other men "She's with me."
As far as picture taking go, men can be camera shy, or feel like they are taller and should be in the back. They may also just be used to seeing many pictures that way and assume that's what guys are supposed to do for pictures.
As far as tears, men are all across the board on this, just like women. Some men show emotions easily, some rarely ever let anyone see their tears, and most men fall in the middle somewhere.
The more important thing is if the tears are coming at a time when the emotions or events are sad. If so, that's a guy who's more emotionally aware and hasn't learned to hide his emotions. That's usually a good thing, and something most women like.
If he's crying at times that seem inappropriate, it could be a sign of stress or depression.
The best bet it to talk to you boyfriend and ask him "Why do you like to stand/hold me from behind?" or "Why do you let yourself cry at sad movies when other guys don't?" His answers might surprise you.
Thank you. Is the notion of showing possession of the woman conscious or unconscious?
It depends. Some men are very conscious of it, and can get very territorial when their partner is near another man or being looked at by another man. These men tend to be controlling and may be more prone to domestic violence. Most men don't see it as a bad possession, but rather an outward symbol that "we are a couple." Similar to holding hands or sitting close, or other forms of public affection. A few men who are prone to anxiety or lower self-esteem may use this type of display to try to boost their own image and feelings of security (as in "See, she likes me, I can't be all bad"). Or they may need more physical closeness and contact when under stress, such as men who are socially anxious and tend to depend on their partner to stay calm in social events. Physical touch can be a way of soothing their own anxieties.