Discoveries: The Journals of Lewis & Clark

No — you must play dice showing only one Action face on your turn; you can perform several different Actions that use that same face, but you may not perform the exact same Action twice in one turn (e.g., you cannot take two Friendly Tribe cards). (page 5)

No — you are not allowed to use a gray die the same turn you take it; if the gray-dice stock is empty the player with the most gray dice must give you one (ties you choose which tied player). (page 6)

Yes — you must play all prerequisite dice before you play the Journal die, because Journal dice are placed last and are what trigger the Exploration Action. (page 7)

Yes — if you have enough Exploration Actions you may fully explore a second Discoveries card from the Reconnaissance Area in the same turn (maximum two cards per turn), and exploring two cards grants you an immediate bonus turn. (page 9)

After exploration you take back ALL remaining dice from ALL your triggered Actions, re-roll them and place them in your Dice Stock, but those dice must not be played again that turn. (page 9)