Why can't I get the "Dangerous Intersection" achievement?

When I talked about the Dangerous Intersection achievement with Chessica, Chess.com's AI it said:

To have the achievements for the variants automatically unlocked, you have to play those variants from the normal Live Chess server and not from the Variants server.
If you want to play those 4 variants (Crazyhouse, Bughouse, 3 Checks and King of the Hill) in Live Chess server, you just have to go to Play > Play online, then select Custom. Click on Standard to chose the type of game. You will see the 4 main variants there.
Unfortunately, the 2 awards for 4 Player chess (Dangerous Intersection and Battle Royale) can not be unlocked on the site anymore. So that's why.