No, couples are not allowed to be alone before marriage. Once, about 15 minutes before a Tuesday night meeting I was practising my talk in the second school. My fiance was with me. An elder from Bethel? came in and broke it up, telling me it was inappropriate for me to be alone with a woman who was not my wife. It pissed me off a little, so I answered, "Roger, if I want to get laid I can think of better places than the kingdom hall to do it."
Walter