I wonder what information should I put in this very short video?
You should put information and facts that briefly but concisely describe you.
Things I suggest you include may be your educational background (what you studied, where), your professional interests (past projects or gigs), and also some more personal facts, like what is your preferred name, what are your hobbies, etc..
Is there anything specific they are looking for in that video?
Can't tell what their true intentions are, but most likely (and also judging by what they asked you to do), they are seeking a brief introduction and description about yourself, so they can (perhaps?) get a more realistic look-and-feel on what you are in person.
They may show this to the current team, or to the ones deciding on who gets hired, so they can give feedback on potential candidates.
Shall I dress up a suite and tie?
You mention this is a Data Manager position, so wearing suite and tie could be a bit of an overkill. However, I would not go the other opposite and wear a t-shirt of your favorite sports team...
Perhaps a Polo-like shirt could do the trick (remember, it's a 20 sec video you will probably record with your phone or laptop camera).
This also depends on your country and company culture. I suggest you do some research on how they usually dress on that company, specially people in similar roles, and go for that. Perhaps the way the people that interviewed you dressed could give you some clues.
...and if everything else fails, remember that it's better to be over-dressed than under-dressed.