Under what conditions can a flight continue beyond the point of in-flight re-planning?
it’s just a complicated way of saying: you are not allowed to begin an IFR flight either from the ground (“shall not take off”) nor can you file a new one in the air (“continue beyond the point of in-flight re-planning”) unless some weather conditions are met at the destination and nominated alternate(s). 

I other words the “point of in-flight re-planning” is not a decision point, it’s just: the point where we would like to file (re-plan) a new flight plan (in-flight).

And the conditions are the same wether you are on the ground or already flying: either (destination WX > operational minima) or (ALL nominated and required alternates > planning minima)

note that (depending on jurisdiction) most of the times a minimum 2 alternates are required if destination WX &lt; operational minima.


  
  Can I continue flight at the point of in-flight re-planning if:
  "destination APO WX > minima" &amp; "alternate APO WX &lt; minima"
  


if destination > minima, under specific circumstances you might not require an alternate. if still required, it must be nominated and above the planning minima. So answer : probably no.


  
  Can I continue flight at the point of in-flight re-planning if:
  "destination APO WX &lt; minima" &amp; "alternate APO WX > minima"
  


if destination &lt; minima, you will most likely require 2 nominated alternates and the must BOTH be above planning minima. Shory answer: yes