Not all pawns that can't advance are backward pawns. Take the example above of pawn on 4 v. 3, No. 11&12. Neither on the 3rd rank would be considered backward pawns, even though they cannot advance without capture. They have pawns behind them that defend them.
On page 86, H&M-S detail what is an acceptable backward pawn. Using the reverse, we can deduce that if:
- It cannot be safely advanced before it is fixed;
- The opponent can open (half open) the file to attack it frontally; or
- It cannot be sheltered by an outpost ahead of it on the file.
No. 52, p. 82, shows a typical examples of backward pawns. The Queenside example shows (to my mind) a true backward pawn. It is at the base of a pawn chain (this is where backward pawns usually are). If it advances, it dies. It is fixed. The Kingside example I would not classify as a backward Black pawn, but instead a Kingside Majority for White. I think on the right there is only one point to be given, and it would be a plus point for White. However, because of the left side of the board, there would be a minus one for Black because of his backward pawn. Thus White has a net of plus two.
I would count the above pawn as backward because it cannot advance. I would also count a pawn as backward if it is at the base of a pawn chain (even a 2 pawn chain) and can be attacked. This is where your COA Control tab comes in handy. Sometimes a pawn is not colored under this tab, and that means it is not under attack. But if the opponent`s color causes a tie or is a solid color, watch out! You could lose that pawn.
A backward pawn, because it has no pawn behind it to defend it, needs to be defended by a piece. This crimps that player's game, thus a minus point.