If I wielding a reach weapon (like a Bardiche) and my foe is adjacent to me, then CaGM won't work, correct?
Likewise if I am wielding a normal weapon (like a Falchion) and my foe is attacking me with reach (as any Large or larger creature is like to do), CaGM won't work then either?
Short answer: correct on both counts!
If I wielding a reach weapon (like a Bardiche) and my foe is adjacent to me, then CaGM won't work, correct?
Come and Get Me (Ex): "While raging, as a free action the barbarian may leave herself open to attack while preparing devastating counterattacks. Enemies gain a +4 bonus on attack and damage rolls against the barbarian until the beginning of her next turn, but every attack against the barbarian provokes an attack of opportunity from her, which is resolved prior to resolving each enemy attack. A barbarian must be at least 12th level to select this rage power."
If the enemy provokes an AoO from you, but is not within a threatened square, then you can't make that attack of opportunity.
Likewise if I am wielding a normal weapon (like a Falchion) and my foe is attacking me with reach (as any Large or larger creature is like to do), CaGM won't work then either?
It still does exactly what it says. But if you don't threaten them, you can't take the AoO.
Come and Get Me works under both conditions, but because you can't actually hit them you cannot take the Attack of Oppurtunity.