As of right now, there is no official exact release date, aside from confirmation of summer 2019. It is expected to hit the internet roughly mid-July, or possibly in August. Something as highly anticipated as WoW Classic could launch with weeks of notice and still break records. As of April 21st 2019, World of Warcraft Classic has entered internal employee alpha testing.
A demo of the game was available at BlizzCon 2018, and was downloadable on home computers for anyone who purchased a BlizzCon ticket or virtual ticket. The servers became available when Opening Ceremony started at BlizzCon 2018 and was set to end on November 8, but was extended until November 12. Players started at level 15, and the only available zones were Westfall and the Barrens. It was based on patch 1.13.0, essentially patch 1.12.0 ported to a modern infrastructure. The first day of the demo, there was a playtime limit of a cumulative 60 minutes with a cooldown of 90 minutes, applied through the BlizzCon Exhaustion debuff. The debuff was removed on the second day of BlizzCon 2018.