Most of those requirements need to be done in the same round otherwise they wont count.
What @xxxC🤭lBr33zExxx says. It's like this:
Express Train:
2 assist ribbons and 10 kills inside the Metro must be achieved within the same round.
Dead Stop:
You must raise/lower Caspian gate and get a shotgun ribbon in the same round.
Now, about Big Splash, it's a more problematic one... about flood gates from Sunken Dragon, which gametype did you try to activate them on? CQ Large or something else? Also, aside from that, did you try to get kills while swimming already?
Also, unfortunately I don't think that contacting a dev will be possible... devs are not present on AHQ. In the past the best way was participating in CTE subreddit, but CTE is pretty much over now, so it will not work.
