Simple RAW for 3.5: 38 pages, and I still don't know how to play D&D

[Vaern]

Q1
One of the 5 ways to enter Warshaper is
"Polymorph as a spell-like ability (astral deva, planetar, solar, couatl, marilith, bronze dragon, gold dragon, silver dragon, efreeti, leonal guardinal, night hag, ogre mage, pixie)."

Most of these creatures don't have polymorph as a spell like ability. The monsters with change shape are covered elsewhere but how do the dragons (who have alternate form) and leonal (which doesn't seem to have any kind of shapeshifting) qualify for warshaper?

A1

None of these creatures qualify for the warshaper class due to having polymorph as a spell-like ability except for the planetar*. The dragons, leonal, marilith, and pixie do not qualify at all. All of the others qualify by nature of having the change shape ability.

A) The listed dragons did get polymorph self 3/day as a spell-like ability in 3.0. It's very likely that these dragons' listings are simply an oversight that slipped through the cracks, as Complete Warrior came out just a couple months after the 3.5 update was released which replaced the dragons' polymorph SLA with their alternate form supernatural ability. There was a time when they could have qualified for the class via SLA, but they no longer meet that requirement.

B) Every other creature on the list except the dragons did have polymorph as an SLA in their 3.5 Monster Manual descriptions. The errata removed polymorph SLAs from a lot of creatures including (but not limited to) the astral deva, astral deva*, solar, couatl, marilith, efreeti, leonal, night hag, ogre mage, and pixie. The SRD shows information consistent with the errata, so if you're checking these creatures' descriptions using resources readily available online you won't see polymorph on any of these creatures. It's worth noting that even the one creature that still has polymorph probably shouldn't, but seems to have slipped through the cracks due to an apparent error in the errata*.
Most of the creatures that had polymorph taken away were given the change shape supernatural ability to replace it with, and therefore still qualify for warshaper despite losing the SLA. The leonal, maralith, and pixie simply did not get anything in exchange for losing polymorph and therefore no longer qualify for the class.

Spoiler: *

Show

Angel, Astral Deva
Monster Manual, page 11
Remove “polymorph (self only)” from spell-like abilities.
Add the following entry:
Change Shape (Su): An astral deva can assume the form of any Small or Medium humanoid.


Angel, Astral Deva
Monster Manual, page 11
Remove “polymorph (self only)” from spell-like abilities.
Change Shape (Su): A planetar can assume the form of any Small or Medium humanoid.