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

[Beni-Kujaku]

A 116 You're not the one casting the ability (and it's not even cast, since it's just releasing the stored energy in your Companion. Anima Mage or Illumian do nothing.

A 117
The discrepancy is because the lore is very clear that only humanoids should be able to become dragonborn, thus saying that they remain humanoid and saying that they retain their type should have meant the same. That said, they did not include this restriction in the actual template, and thus RAW there can be non-Humanoid dragonborn. There was an FAQ on this exact subject saying : "A warforged who becomes a dragonborn would be a construct with the living construct and dragonblood subtypes.". A nonhumanoid dragonborn of Bahamut retains their type and subtype.

A 118a "A single tooth or claw from a dragon can be crafted into a light weapon of the same size category as the dragon, a one- handed weapon of one size category smaller, or a two-handed weapon of two size categories smaller. A single dragon's body can provide enough material for up to twelve weapons."
You cannot create items of wildly different size from the dragon (in effect, you don't cut a single fang into multiple weapons). Thus, medium dragonfang arrows (light weapons) can only be created from the corpse of a Medium dragon, and only twelve of them can be created from a single corpse. Using the fangs of a Large dragon would just make impractical, unuseable large-sized arrows.

A 118b Unclear, ask your DM.

A 119 The creature can choose which additional natural attack it makes. However, Haste does not negate the "secondary" penalty. "The attack is made using the creature’s full base attack bonus, plus any modifiers appropriate to the situation."

A 120
No, undead creatures do not retain the benefits of their grafts, as the grafts die when the creature dies (from RotD). It's weird to say "die" when talking about Undead grafts, for example, but the principle is the same. A graft is unuseable after death, unless resurrected. You cannot harvest grafts on a dead creature, and you cannot harvest grafts before the creature dies, otherwise the graft isn't considered part of the body anymore when the creature dies, and isn't reconstructed by Resurrection. I don't know of a legal way to make this work.

A 121 Except during the casting, an SLA works exactly like the spell it replicates. A spellblade with Plane Shift would block both a wizard casting plane shift to shift the bladebearer, and a Couatl trying to do the same. With the Magic-Psionics transparency, it is also absolutely possible to craft a Spellblade that protects against a psionic power. However, remember that Plane Shift and Psionic Plane Shift are still two different "spells", and that a spellblade that protects against one would do nothing against the other.

A 122 As far as I know, there is only one mention of riverine in all of 3.5, and this mention contradicts itself. Thus, ask your DM on if you should round up or down the deflection bonus. What is less ambiguous is that a +X armor would also increase the deflection bonus (a +4 riverine full plate would give +6 armor and +6 deflection bonus to AC.