Kegging Cider Question

The Aplephine is ready to keg, but I have decided that I will back sweeten it, however I know that I can't serve this fresh aplephine for aonther 5 or 6 months. Should I transfer to the keg and let it sit for 5 or 6 months, then open it up and add a can of apple juice concentrate? I could add it at the time of kegging, but I am afraid it will once again ferment out the additional sugars. I do have some pottasium sitting around that could be used, will someone help me?

Use pot K and campden to kill the yeast, keg it and age it for however long you want. then sweeten to taste and carb. Or you could sweeten, then age.

Do I need to use both, I thought I could use Pot all by itself to kill the yeast?

Do I put the Pot in the carboy or in the keg?