Confused about ContainmentType in Collision detection

[ocean2oo6]

hi all,
i do something just like appCollisionInterfaceDemo and it works fine. But i.m confused by some steps throught this process:
cWorldX.PerformDiscreteCollisionDetection();
for (int i = 0; i < cWorldX.Dispatcher.ManifoldCount; i++)
{
Question 1:
Manifolds are generated by a pair of collisionObject? then can the same pair of collisionObject
results in more than one Manifold?
Question 2:
when does bullet update and clear Manifolds?

contactManifold.RefreshContactPoints(obA.WorldTransform, obB.WorldTransform);
int numContacts = contactManifold.ContactsCount;
for (int j = 0; j < numContacts; j++)
{
Question 3:
i guess numContacts is current Manifold's contact points.
and can i get the ContainmentType(Contains,Intersects or Disjoint) about this Manifold?
}
}
I'm sorry to ask so basic or silly question. but i cannot find the answer for these and really not sure.
thanks for reading!