I see you have a flag halyard going to the center of the starboard spreader but the lines that you show in the other pictures seem to lead to the top of the mast as if it was intended as a spare halyard. Waterwaves is correct 3 strand line has to much strech to be used as a halyard. That is not factory installed so perhaps the PO may helep clear what he used it for.
You can see those lines coming down from the top of the mast. There are four sheaves at the top. I would consider the 3-strand as messenger lines for installing good halyards. In the front it would be used for flying an asymmetrical. I use the aft one as a spare by attaching it to the topping lift for control of the boom.
I agree with Ed that they are probably there as messengers for good halyards, but if they are coming out of the front sheaves at the top of the mast, even good halyards can only be used for as jib and spare. You would not want to fly a spinnaker or even an asymmetrical from a halyard exiting below the head stay as you could not gybe it without messing it up in the headstay itself. A spinnaker halyard is normally run to a sheave straight out from the mast top, in front and above the headstay.