I can’t imagine what is confusing about the answers you’ve gotten other than the fact that they probably weren’t what you expected/wanted to hear.
It’s pretty simple. The plane ends the turn in whatever territory or seazone it ends its movement in. The plane can not be moved from land to sea during mobilization of the carrier. If it can reach a seazone in NCMs it can end its turn there and you can use a new carrier in that sz as the landing place.
In your example, because going UK to sz5 to sz2 is 5 movement, you could not end the turn with the fig in sz5 without either getting LRA tech, or by forgoing the fig for the attack on sz5.
IIRC, for Revised I believe the out-of-the-box (OOB) rules allowed you to move the fig from land to a new carrier during mobilization, but the Larry Harris Tournament Rules (a.k.a LHTR -the ruleset used for league and tournaments at most online sites, including this one, and other events to clear up a lot of vague, unbalanced, and inconsistent items in the OOB rules) used a rule akin to the AA50 rule above.