Kefir culture, which contains both types of microbe, is perfectly happy turning sugar into alcohol into vinegar inside a sealed vessel. If you wanted to stop it, you would need to evacuate the vessel or fill it with an inert gas. If you also had a microbe in there that split water into H2 and O2, you'd have no chance at all at more than about 0.5% alcohol by volume in there. I'm not aware of any existing kefir culture that has such a microbe in it, but once one was adopted it would be near impossible to get rid of it while saving the rest of the culture.

The boiling happens with beer, mostly. With wine, you're usually relying on the yeast that naturally occurs on the surface of the grapes, so if you boiled (or pasteurized) it, there would be no fermentation unless you added additional yeast. That sometimes happens, because some people prefer consistency to authenticity.

Home brewers use fermentation vessels that allow gases to escape through a liquid trap and the whole process is done at positive pressure. You can bet your ass that those vessels are thoroughly sterilized before each use.

We may be talking past each other here.