as the imperial player i know that my opening group can consist of the number of non unique cards stated (until unique's are unlocked)

do elites also have to be unlocked?

and are the units that are on the board at the start of the missions considered part of my open group? and re playable any time they would die off?

for example, if all 3 probe droids (1 elite and 2 regular) are on the board at the start of the mission, if one of them dies am i able to bring it back with the threat if my open group of hidden cards consists of 2 sets of stormtroopers?

Non-unique elites can be used without earning them. Earning applies only to unique deployment cards (Villains). (Rebels need to earn their non-unique Allies though.)

You start the mission with Open groups as your deployment card hand. Any non-unique deployment cards return to your hand when the last figure of the group is defeated. You can deploy any deployment card in your hand by paying the deployment cost during an optional deployment.

The deployment cards have no memory. Once defeated, a deployment card is just a deployment card. It does not matter whether it came from initial groups, open groups or reserved groups. Reserved groups can only enter the game from events, but once deployed and defeated, you can use any non-uniques just like any other non-uniques.

So if all 3 Probe Droids are in the initial groups and they are defeated, they return to your hand and can be deployed later.

thank you