Answer:
The answer is a double-blind study.
Explanation:
A double-blind study is a research method in which neither the participants or the researchers are aware about which group is receiving the treatment. This is done in order to avoid biases such as the placebo effect, as well as preventing accidental cues given by the researchers.
The greatest advantage of this approach is its high validity.
Depends on what relationship you have with this "other guy". If he's just a friend to you it shouldn't even be considered romance unless you flirt or hook up. If he is a romantically relationship than you are definitely cheating.