Two questions...

The Emperor is on a ship with 1 evade die. He changes the result to Evade. Can Crack shot remove it? (Emperor says it cannot be modified, so, I'd guess you could not use crack shot?)

Now, the Emperor is on a ship with 1 evade die. That ship rolls an evade. Can the Emperor 'modify it' to be an evade so it cannot be removed by crack shot?

Cancellation is not actually a modification of the dice, so Palpatine's protection doesn't apply.

The second one is an interesting question without precise definition - the rulebook defines changing dice: "To change a die result, rotate the die so that its faceup side displays the new result."

Does it have to be a different result? Unclear... but since the first issue doesn't work, probably not worth worrying about.

In short. Yes. No.

Thank you!