Making my own resource pack

1 – Can I make multiple textures for entities? Let’s say I want my world to have dark wolves and white wolves. Is it possible to make it without using any mods and only textures? Or am I bound to only have one texture per mob? (EDIT: Can I specify the rarity of each of these textures spawning?)

2 – Mob texture animations. I know it’s possible to animate block textures like furnaces, but when I attempted to do the same with a mob texture it didn’t work. I duplicated the texture, put the first frame on the top, the second frame on the bottom, copied and pasted the .mcmeta file from the furnace animation, renamed it to match with the entity file I attempted to animate, and the result was a glitchy texture that wasn’t animated at all.

BONUS question – I’m making this texture for fun, but it would be awesome to see it on the Switch. Would it be at all possible? Or am I only allowed to use it in the Java version?