I want to start playing for the first time, and I'm very confused. Super stupid questions below

The best place to start as a new player is the anniversary edition, right?

I'm not quite sure if the game is currently in its classic form or if the first expansion has already been released?

If I start now, will I be able to play the expansion later with the same character, or will I need to create a new one?

I also heard that the developers removed some classic quests in the modern version of the game. Is all the old content still there in the classic anniversary edition?