Can you cast Spells not in your book's spell lore?

[Belathor]

So this specifically came up with the sylvaneth warsong revenant. Contention 1 was that the aos app warscroll is not correct and the broken realms kragnos is the correct one but regardless.

 

On the warscroll it says the revenant knows all sylvaneth spell lore spells. If taken in cities of sigmar can it cast those spells? 

This has some weird implications like the spell lores now say "Sylvaneth wizards and unique unites only." and warsong rev is a sylvaneth wizard but in cities of sigmar. The lumineth spell lore also says "Teclis etc only" well teclis in settlers gain is teclis only and can he therefore cast those spells?

 

Is a spell lore only available to your allegiance even if you know those spells?

[EntMan]

It says on the warscroll that they can use spells from Lore of the Deepwood, warscroll overrules tome/core rule when there is a conflict (unless specifically stated) so the Warsong Rev gets the Deepwood spells.

(But note that Verdant Blessing is a Sylvaneth faction spell but is not a Lore of the Deepwood spell so allied and coalition Warsongs don't get that particular spell.)