What kind of creatures bosses (Eagle King, Lord of Darkness, or Dragon King on Ending card) are?

Can I use a spells or Objects that targets Enemy creature, or only character. Can I turn them to toad before battle?

Additional question about Dragon King:

When character on Crown of Command rolls 3-4, then all characters sequentially attacks the Dragon King. That mean all characters on board or only all characters on Crown of Command?

Took this from the Blood Moon rules, but it is also found in the rules for other expansions that feature alternate endings:

"None of the creatures in the Inner Region (nor any of the
Alternative Ending Cards) can be affected by any Spell.
They also cannot be evaded." (p. 4)

But how about Dungeon and Highlands? In rules we have only:

Fighting the Eagle King is conducted according to the normal
rules governing attacks, save that the Eagle King cannot
be evaded and only characters may attack the Eagle King;
Followers, Spells, or Objects cannot fght in a character’s
place.

This mean I can't use any spells on The Eagle King and The Lord of Shadows or I can still turn them to toad?

Also can someone list what actions I can do in fight with Bosses (on Dungeon, on Highlands and on Crown of Command) and what I can't?

Bosses on the expension boards are considered creatures and as such can be affected by spells, the only exception if I remember correctly is that you cannot evade it. Using Toadify on the Lord of Darkness is a good strategy to win the game, if the spell works

Enemies- if something refers to using it on an enemy, this only applies to adventure cards on the board which say enemy

Creatures- creature refers to all enemies, and all board space encounters (eagle king, trolls in ruined cave, drunken farmer in tavern even)

Characters is pretty obvious

So if it says you can use it on characters and creatures, you can use it on anything (except inner circle creature encounters)

if it says on an enemy, it is only really used on adventure cards