AOE 2 HD/DE expansion pack (QUESTION)

I already own AOE 2 HD base game, but i want to buy the expansion packs (Rise of Rajas, The Forgotten, The African Kingdom) and AOE 2 Definitive Edition as well.

I want to know if i purchase these expansion packs now, will they work in AOE 2 DE as well , i.e. All of the civilizations in expansions will be available for me in DE when i purchase it or not?

And if i buy DE before buying the expansion packs, is there any additional civilization available in that base game?

I have played HD base game for long time, and I want to play some new civilizations. Please help.!

Thanks in advance.