The two words were distension and dissention.
The latter word is treated as rare because it is a rarely used variant of dissension, which is a common word in our lexicon, though I don't know if it's ever been playable in a puzzle.
Since each puzzle starts simultaneously around the world, it starts at a different time, and sometimes on a different date, in each time zone. So the clearest way of identifying a puzzle is by referencing the date displayed near the top of the layout - e.g. 10-letter puzzle for 15 May.
