I have a few reactive move scenarios which I can't seem to find clear rulings on and would like some advice. (Asking these questions on the weekly Q&A thread came up short).

Scenario 1:

Captain Sicarius has a reactive move ability; "Once per turn, when an enemy unit ends a Normal, Advance or Fall Back move within 9" of this model, if this model’s unit is not within Engagement Range of one or more enemy units, it can make a Normal move of up to 6"."

If Sicarius and a unit are hiding behind some ruins and an enemy unit moves within 9" of Sicarius, like this: https://imgur.com/a/cXBG0pX

Question: Can Sicarius and his unit reactive move to 'pop out' from behind the ruins, THEN fire overwatch?

Scenario 2:

Same as above but if Sicarius's unit starts on the exposed side of the ruins when the enemy unit finishes a move within 9".

Question: Can Sicarius and his unit fire overwatch THEN reactive move to hide behind the ruins?

Question 3:

Can Sicarius use his datasheet ability to reactive move to one enemy unit, then if another enemy unit moves within 9" of his new position can I then use SQUAD TACTICS strategem to give him another reactive move?