The die is rigged, so "not 3" is not a possibility. Ruling out those branches of the tree, there are 4 possible outcomes, one of which is the desired outcome. So the probability is 1/4.
A fair die has six sides that are equally likely, so the probability of rolling more than 2 is always 4/6. The outcome of the first roll does not effect the outcome of the second roll.
The correct answer is: if is a root of , then is also a root of .
In fact, every polynomial has real and/or complex solutions. If all solutions are real, we're good. But if not all of them are real, then the complex ones come in couple of conjugate solutions. Since and are conjugate complex numbers, if one of them is a solution, the other must be as well.