Actions and rights which came into being but were not exercised before the effectivity of this Code, shall remain in full force in conformity with the old legislation; but their exercise, duration and the procedure to enforce them shall be regulated by this Code and by the Rules of Court. If the exercise of the right or of the action was commenced under the old laws, but is pending on the date this Code takes effect, and the procedure was different from that established in this new body of laws, the parties concerned may choose which method or course to pursue. (Rule 4)