K-sorbate and Potassium Sorbate are same? Use Sorbate to "kill" yeast?
AND once yeast is dead, the sweet will stay in wine... but how do you carbonate and keep sweet in? If you need yeast cells to carbonate, dont they keep going till surgar is gone...or till top blows?
Sorbate doesn't kill yeast. It inhibits yeast reproduction, so it's used after fermentation finishes to prevent the sweetening agent from fermenting.
If you use sorbate, you will not be able to bottle carbonate.
It's easy to make a dry wine or cider. It's easy to make a sparkling dry wine or cider. it's easy to make a still sweetened wine or cider. It's very difficult to make a sparkling sweetened wine or cider without kegging gear.
If you want to stabilize, the cider/wine needs to be completely clear and racked off the lees (so that there are few yeast still in suspension and no lees at all) and into a mixture of campden (sulfite) and sorbate. The usual dose of campden is 1 crushed and dissolved tablet per gallon, and for sorbate it's 1/2 teaspoon per gallon. It can be mixed in a little water, and then the cider/wine/mead racked into it. That will ensure no fermentation will occur.
Sorbate doesn't kill yeast, but it inhibits yeast reproduction. That's why it doesn't "work" if you add it to a fermenter that has billions and billions of yeast, as the yeast doesn't need to reproduce then. Campden doesn't kill yeast either, but sorbate works better in the presence of sulfites so it is added along with the sorbate.
This is cider, not wine, but it's the same process:
https://www.homebrewtalk.com/showthread.php?t=508303
A beginner write up may be helpful to answer these questions.