Separate property is: 1) all property, real and personal, acquired by either party before the marriage; 2) all property acquired during the marriage by bequest, devise, descent, survivorship or gift from a source other than the other party; 3) all property acquired during the marriage in exchange for or from the proceeds of sale of separate property, provided that such property acquired during the marriage is maintained as separate property; and 4) that part of any property classified as separate property.