So we have the Enterprise C going into the future. Was that future an alternate timeline, or a prime timeline that was later corrected, so to speak, when the E-C went back into the past...or the timeline that it was supposed to be in. It always confused me as whether the timeline was an alternate timeline, or an altered prime timeline. So what about Guinan? Did she just know that something was wrong with the current timeline?
Obviously time travel rules have invariably been whatever fits the story, I lean towards the episode beginning with 1) an original timeline, continuiting with 2) a heavily altered timeline, and finishing with 3) a restored timeline close, but not quite the same as the original.
The differences of the third timeline to the first would include:
-First and foremost, a Tasha Yar from 22 years in the future, having a half-Romulan daughter Sela, and whatever other impacts either of their lives had.
-Castillo commanding the Enterprise-C instead of Garrett and whatever different command decisions he would have made.
-The "C" crew being aware of the future (if an altered future) and some knowledge of role their absense had in shaping that future.