Screw Yourself: A remarkable percentage of people who have access to forking technology try this at least once or twice, with or without gender-flip, just to decide if that qualifies as sex or masturbation.
(Hint: it’s sex. Narcissistic, quasi-incestuous, oddly symmetrical sex.)
Opposite Sex Clone: Fairly trivial, for an Imperial level of bioengineering (X-doubling, made easier by earlier eugeneering out of bad recessives, or synthetic X), and done (a) on a relatively infrequent basis for reproduction and (b) rather more often to produce spare (empty) bodies of the other sex. See Gender Bender.
It is also probably worth noting that “opposite” is a little inaccurate, since “herm” and “neuter” are among the common possibilities…
(If you’re planning to Screw Yourself, on the other hand, you’d better take option (b) and occupy your clone’s brain with a fork of you, since if you make a new person and you’re the one who raised them, you’re going to run straight into major consent problems of the intergenerational incest kind, which is very, very much an ethical and legal no-no.)