a) I move onto a full hex and automatically the unit is activated, paying the cost of the MD that enter plus the cost to move of the unity. Example : an unit that movement cost 1 PA, enter how reinforcement into a light jungle hex ( DM +1 ), that means that the unit is activated and when i place into the board only would do with 5 PA ?
b) If a want to enter a reinforcement, a place it an a valid hex, without pay any PA or PAM ,and later if a want to do anything with the unit i activate it.
You activate the unit that is off the board and pay any cost to enter the hex, so "A" would be correct.
5.5 Reinforcements When a Firefight calls for reinforcements these units may come into the game on that Round or later Rounds. If the reinforcements enter on a later Round, they must still enter on the same hex(es) as specified by the Firefight.
Units move onto full hexes when entering a Firefight. Half hexes are ignored. The move can be made with a Unit AP, Opportunity, Command or Card Action.
If an enemy unit occupies an entry hex, the reinforcements may shift their hex of entry by up to 2 hexes.
Multiple units may enter the map simultaneously using a group move (10.1.1) or while being transported (22.0).