The icons for the events are shown on the map, but the person who made the video never travels to any of the event locations so I cannot say for sure (but I assume no). It all depends on how vigorous Mihoyo has been in purging older events from the game's files to reduce the footprint for mobile players and the general state of the game/server interactions and how well they're being emulated. If I had to guess, I'd say there's a possibility of the original Dragonspine event being possible to play through in the future (I don't know if the emulated server can do quests/dailies properly, or even how the game itself handles event/version data). I'd wager due to Dodoco Tales being a one-off time limited map, that would require some tweaking of the actual game files as well as a copy of the game from a year ago when the event was running because there's no way that wasn't completely purged. Same for the recent Three Realm event.
At the very least, the unique map icons from prior versions have stuck around. It may be the case that only the audio/cutscenes have been purged as they would have the greatest footprint and the event text/mechanics have stuck around in the game archives. Hard to say without ripping apart the game to find out. The only things I can confirm via the video that are working fully are combat, leveling characters/artifacts/weapons, wishing, and worldwide teleportation(though it just immediately teleports you to location before everything has loaded in).
I'd love to play around with this, but unfortunately I just don't have the time to do so this week. It's quite bare bones at the moment, as
this test video shows a complete lack of item/monster spawns, and I imagine all chests/puzzles are either missing or don't work as well. No idea about domains/resin/bosses, but I'd guess they're probably not working yet. So overall, a respectable start but still have a long way to go before it's a replacement for the game. But if you want to fight one of Childe's forms in the middle of Mondstadt with characters/weapons you don't own...you can do that, and you can do it right now.