Combat maneuvers are not new. They are an amalgamation of existing 3.5 actions under a unified resolution mechanic. While a few tweaks have been made to the exact functionality, the language of Attack of Opportunity provocation has not changed, here, or anywhere else.
The Strike Back feat gives you the ability to strike a limb in specific circumstances. This means that you cannot strike a limb without that feat. If you cannot reach, the squares a creature occupies, and you're not using Strike Back, you cannot make a melee attack against that creature.
I removed some posts. Clearly this thread is not going to come to a conclusion anytime soon, so it is locked (especially since we're now apparently engaged in a debate about the nature of rules debates at this point.)
If you really want to continue talking about it, make a new thread.