Let's look at the text itself.
Players Handbook page 233 said:
Freedom of Movement
Abjuration
Level: Brd 4, Clr 4, Drd 4, Luck 4, Rgr 4
Components: V, S, M, DF
Casting Time: 1 standard action
Range: Personal or touch
Target: You or creature touched
Duration: 10 min./level
Saving Throw: Will negates (harmless)
Spell Resistance: Yes (harmless)
This spell enables you or a creature you touch to move and attack normally for the duration of the spell, even under the influence of magic that usually impedes movement, such as paralysis, solid fog, slow, and web. The subject automatically succeeds on any grapple check made to resist a grapple attempt, as well as on grapple checks or Escape Artist checks made to escape a grapple or a pin.
The spell also allows the subject to move and attack normally while underwater, even with slashing weapons such as axes and swords or with bludgeoning weapons such as flails, hammers, and maces, provided that the weapon is wielded in the hand rather than hurled. The freedom of movement spell does not, however, allow water breathing.
Material Component: A leather thong, bound around the arm or a similar appendage.
Okay, so, does it protect from Hold spells? Yes. It's a form of paralysis. Note that a Held person is immobile, even if allies try to move the person. They are frozen in place. They can still think, it's just their body that can't move.
Does it allow for people to drop through the earth to the fiery center? No. It prevents magical impediments, not physical ones. Walls and floors are still there, as is the armor and shields of opponents. (If someone tries to argue that they should be able to attack and pass through such things, then rule that they also pass through the person inside, without resistance, and without doing any harm.)
Does it allow them to walk through
Force Cage or
Wall of force spells? Hmm. Is it a Grapple? No, it's a Wall. But it's a magical one, so suddenly the rules look a little gray.
Wall of Force says that it stops everything, so that suggests that it stops the FoM character, and the WoF and FC effects don't resemble a grapple or entangle effect. That is, they don't stop a person from moving their arms, legs etc, they simply act as a barrier. So on the balance I'd rule that the various Force effects work against
Freedom of Movement.
Does it let someone slip a hold or escape a grapple? Yes, it explicitly says so.
What about Swallow Whole abilities? Since they're resolved using the Grapple mechanic, and the recipient always wins when defending in a Grapple contest, I'd say they shouldn't become someone's snack.
Does it let someone escape manacles, ropes, leg irons or similar restraints? No (surprise). It says you succeed on Escape Artist checks specifically to escape a grapple or pin. So lock the cell door and they're locked in just like anyone else.
What does it do in the water? It allows the recipient to move and act normally, and swing weapons that would normally have a problem due to water resistance. This extends only to melee weapons, swung or hurled. Bows, on the other hand, still get messed with, as they aren't "hurled".
Taken literally, word for word,
Freedom of Movement is incompatible with
Water Breathing. I'm sure they meant that it doesn't "include"
Water Breathing, but as written it actually disallows it.
Hmm. Learned something new today.