1.16 - this only applies to people who are applying for an Unmarried Partner visa, as that visa has a requirement that you must have lived together for 24 consecutive months before applying for the visa. If you are married and are applying as a spouse, you do not need to answer this question.
1.18 - if you have not legally lived together in the same country as each other (i.e. one of you has a visa to live in the same country as the other, like a student or work visa), then you say no.