-event 6: Is it legal to move away some of the units already involved in attacking Alcazar in order to satisfy event`s requirements to move >= 6 steps EVERY turn? I mean kind of shuffle them in and out?
I'll talk to Javier on this, but my feeling is that once you have 6 steps of units within 2 hexes of Alcazar, you would be exempt from moving additional units there (but could not leave less than 6 there). Good catch on this, since - technically - there is nothing stopping you from "shuffling" like you mention.
-evacuation movement: If I evacuate Northern units to 3324 are they OOS/ can they move within central zone? Northern units trace from their own USS only according to 9.8.
Good catch, this should ONLY apply to regular Republican units, not Northern Republican Units. This is for any Republican units that can cut-off isolated by a drive to Barcelona, they can reappear at the French/Spanish border in hex 3324.
-Northern reinforcements placement: They can be placed in adjacent and controlled hexes next to their capitals but, though not mentioned, I think they still can not be placed in EZOC/ OOS/ overstacked -like normal units, right?
They have the same restrictions as regular units, yes. EZOC alone does not stop placement of reinforcements - only if the hex is enemy controlled (EZOC does not change control of hexes). See 7.8.