If you don't exceed the alcohol tolerance of the yeast (having them die of alcohol poisoning, so to speak), the yeast will be alive and well although dormant.
In order to sweeten a wine, you'd rack as needed and wait to the wine is completely clear and no longer dropping any lees at all. Then you would rack the wine onto a solution of campden and sorbate (1 crushed campden tablet per gallon and 1/2 teaspoon of sorbate per gallon). Neither kill wine yeast, but sorbate inhibits yeast reproduction. It works better in the presence of campden, so that is why the campden is added. Since there are still yeast even in the clearest wine, adding the sorbate means it can't reproduce and probably won't be able to restart fermentation. It's not a guarantee, but it works pretty well in a clear wine that has been at FG for a long period of time.
Otherwise, pasteurizing the wine is the only real way to kill the yeast still in solution. That's usually not practical.
Some people will feed the wine more honey or sugar, so that the yeast will start to do of alcohol toxicity. But that is sort of a crapshoot, since wine yeast strains can easily push 18% or more in a happy environment. Which means you'd have sweet hot rocket fuel before the yeast would finally die off.
Cold stabilization also helps. What I mean is if you have a wine that is finished, but still dropping lees, you can put it someplace cold (in the low 40s) and that will encourage more yeast to fall out. Once it's completely clear, it can be racked off the lees and then stabilized with sorbate and campden. That usually works pretty well.
over 10 weeks and does it also depend on the strain can some survive longer than others.
