If someone lists me as a friend, will they see my Friends-Only entries?
No. In order for someone to see your Friends-Only entries you must add him or her to your Friends list and he or she must be logged in.
There is no other way for someone to see your Friends-Only entries. If someone adds you to their Friends list, for example, that does not enable them to see your Friends-Only entries. Note that if you are logged in then you will still be able to see these entries on the Friends pages of such people. This, however, does not mean that they can also see the entries.