In the case of doubt, it is not Kidush Hashem. It would seem loke a "chance" of allegedly earning Kidush Hashem. Even if after the act, the doubt was uncovered in such a way that if in the first place it was known, a Kidush Hashem would have the right act, it still does not count as Kidush Hashem.
I don't know if it would be considered suicide really, or if there is such a thing as a suicide in Shogeg...
NOTE: Kidush Hashem is indeed required in the three cases mentioned in the question ("idolatry, murder, or gilui arayos"). BUT, altough a Machloikes, according to some Rishonim like the Smak (מצווה ג) and the Toisfos (עבודה זרה כז:), and so in the Rosh and the Tur, it is spcifically stated that if a Jew wishes to do a "Mesirus Nefesh" on other Mitzvos, he (is not obligated to bet) can. The Smak even says that it is "Midas Chadidus".