Yes, either X happens or X doesn’t happen. P(X) + P(~X) = 1, so therefore P(X | A) + P(~X | A) = 1. Both formulations are stating the probability of X. But one is adjusting for the probability of X given A; so either X given A happens or X given A doesn’t happen (which is P(~X | A) not P(X | ~A)).
Yes, either X happens or X doesn’t happen. P(X) + P(~X) = 1, so therefore P(X | A) + P(~X | A) = 1. Both formulations are stating the probability of X. But one is adjusting for the probability of X given A; so either X given A happens or X given A doesn’t happen (which is P(~X | A) not P(X | ~A)).