Can I play a Mission card and go on an attack even if my X-Men Strength is less than the Villain's?
Yes. There may be situations when you won't know what your total Strength will be until you've played a Mission card. If your X-Men Strength is not as high as the Villain's, simply discard the cards and don't roll any dice. This does count as your attack, though.
When a Villain is attacking my X-Men, can I use any of my X-Men's Mutant Powers if a 1 is rolled?
Yes. When you are the defender, all of your X-Men are in the battle even if they're tapped.
If I play two Power-Ups that reduce the Strength of the attack color by 1, is the attack now reduced by 2?
Yes, each Power-Up card is treated separately.
Can I use an X-Man or a Villain's Mutant Power after an attack that eliminated them from play?
Yes. Let's say you attack Juggernaut with your X-Men and eliminate him. If you rolled a 1 in that attack, Juggernaut's Mutant Power is activated and he will attack you back before he is taken out of play. Or, let's say a Villain attacks your X-Men and Wolverine takes enough damage to be eliminated. You may be able to save Wolverine if his Mutant Power is activated in that attack.
Why is Juggernaut considered a mutant? His source of power is the ruby gem of Cyttorak.
Juggernaut is treated as if he were a mutant for purposes of this game.
If I modify a die roll so that a 1 or a 6 changes, does the Mutant Power that the 1 or 6 would have activated still go off?
No. If you modify the roll before the Mutant Power would have been activated, the power does not happen.
Does Professor X's ability to reroll dice retroactively affect dice rolls that have already been settled, such as a die that was used to activate an A Mutant Power? Specifically, can Professor X's Mutant Power bring back the card Mystique made me discard?
No. Mutant Powers are never retroactive.