Apply database to older game

Just wondering, I am currently still playing Football Manager 2016. Can I still apply the daily data update from 2017 into the game? or is the 2017 daily updates only for the FM 2017 game?

You can, but you won't get the full effect of the changes.

What the data update does is to add onto the existing database. So when you add it onto the FM17 database, it'll be fine. But if you add it to the FM16 database, you'll miss everything between the data the latest official patch for FM16 and that between the latest official patch for FM17. You'll have everything either side of those, however.