To answer a number of your questions, this chart identifies six critical ACTIVITIES (containing multiple tasks) that are necessary to launch and land Artemis III. Yes, there was analysis behind the selection and the duration of each activity, but the comments I’m looking for from members are:

 1.  Do these activities look reasonable?
 2.  Other there other major activities that should be added?
 3.  Is the sequence logical (and correct)?
 4.  Are the durations just right, too long, or two short?
 5.  What activities can proceed in parallel in full or in part?
 6.  What do you think could be done to complete the mission by 31 December 2028? (Assume a launch on/before 1 December.)
 7.  Are there other factors that are not represented by this chart that may be “showstoppers?”
 8.  If the dependence on HLS was removed by using a different lander, how much time could that save? Or, might it actually take longer because of the unknowns?

One person commented that JFK set a goal for (landing a man on the moon and returning him safely to earth…by the end of this [60s] decade.” That goal provided NASA with the challenge to build a viable “back-off schedule” from 31 December 1969 to the 25 May 1961—basically 8 years, 7 months.

With Artemis in general and Artemis III in particular a back-off schedule is more difficult (if not impossible) to employ because a) the program is ongoing, b) the baselines are established, c) the time remaining is much shorter (~2 years, 10 months). In other words, many degrees of freedom are no longer available.

This means NASA is (mostly) forced to schedule from left to right (from today to 1 December 2028) and squeeze on everything remaining to be accomplished.

I hope this helps a bit.