10 years from my last WoW game

Hello, I played WoW when I was young and was one if my favourite games!
Now, today, after a looot of years, I want to play this game again

But, with one peculiarity, I want to increase my lvl of french, italian, deutsch and russian… yes I like languages so much

So, how can I do this? My idea is to join some guilds that are native from France, Italia, Germany, Russia and practice my language with them
But, I've a better idea that is about playing WoW on differents servers like a private french server, private italian server, etc...

Do you know guys if I download the WOTLK 3.3.5a with the new characters models from Legion, and I change realmlist to other server it will work or I will have compatibility problems?

Thanks, hope you can answer my doubts :D