Hi, I'm new to the game and just having my 1st two player game.
1)As a bonus action on your opponents turn do you select two of the dice of their final dice results, or can you choose two dice from any of their 3 rolls? So they roll all 6, before they keep two and reroll 4, can I choose two of the dice they don't keep?
No, you wait for the whole result. The active player does his whole turn and then you can participate.
2) when you roll the 6 dice after one player has finished their turn, you just choose two of those? No rerolls?
Your own turn starts with rolling 6 dice. Then choosing 2 and reroll 4 or them again. It is always the same for all players.