In an introductory note to this chapter, the Kitzur Shulchan Aruch writes that most Jews are already familiar with the prohibited labors of Shabbos and that he is only addressing common situations with which people may not be familiar. Clearly, the laws of Shabbos constitute an area requiring much greater study than this email alone will allow.
80:55 One may not remove the shreds of one’s cuticles that have separated from the around the nail on Shabbos, neither with an instrument, by hand or with one's teeth. If the better part of a fingernail has become separated and is close to being detached so that it causes one distress, he may remove it by hand but not with an instrument. If the greater part of it has not been separated, one may not remove it on Shabbos even by hand. (The same is true for the cuticle - if the greater part of a strip is detached and causes one pain, it may be detached by hand - Mishnah Brurah 328:95. See there to determine what constitutes the greater part of such a strip. )
80:56 We may not pour into vinegar other liquids in order to sour them and make them into vinegar. One may, however, add water to vinegar in order to dilute it - Mishnah Brurah 321:15.)