Can I watch Digimon Tri without seeing Digimon Adventure 02?
As of the first Digimon Tri movie, you would be able to understand everything that goes on if you had only seen the very first season of Digimon Adventures, except for a couple momentary flashbacks involving vague glimpses of the Digimon Adventure 02 Digi-destined, but those flashbacks still make no sense for someone who has seen Digimon Adventure 02 anyways due to how vaguely they were shown.

Update from the second movie:


   You will need to know a little about the conflicts that happens in Digimon Adventure 02 as we see Ken Ichijouji appear, in the present day, towards the end of the second movie as the Digimon Emperor, which is quite contradictory if you have seen enough episodes of Digimon Adventures 02. Strangely however, he never speaks. The reason why he doesn't speak, or why he is even the Digimon Emperor again, is still a mystery until the third movie is released