We are relatively new to Conquest and this came up last night.

Is there a limit to the number of "Actions" a player may perform in a single action window? My buddy had multiple copies of a card at the battle on the first planet. They arrived exhausted. Can he trigger all of those Actions in the first Action Window in the combat phase?

Many thanks for ironing out this one for us.

There is no intrinsic limit on the number of "Action" abilities a player may initiate in a given window. Some actions will specifically include a limit or maximum in its text. Others will have practical limits based on cost/resources, game state, availability or triggering conditions, etc. But these will all arise from the ability's individual text.

Also, there is no rule "turning off" the abilities of exhausted cards. You can initiate the ability on a card regardless of whether it is exhausted or not - assuming you can meet all play restrictions and pay all costs (e.g., an ability that says to exhaust the card in order to pay its cost clearly cannot be triggered when the card is exhausted - but because you cannot pay the cost, not because there is a blanket rule preventing you from using the abilities of exhausted cards).