Glycerin vanilla extract?

I checked the FAQs; my questions aren’t there.

I’ve had some interest in non-alcoholic vanilla extract made by me so am looking into this before I go ham. My questions:

Is this similar to the “normal” extracts—-as in, can I throw some vanilla into the bottle and call it a day, or do I need to add something to it to help the extractive process?

Does glycerin have a finite shelf life or is it infinite like alcohol-based extracts?

Is it its own preservative or do I need to add something to help preserve it?

I’ve seen there are three types of food grade glycerin: palm, soy, and coconut. Which is the favorite overall? I’m leaning toward soy, but am open to feedback on this from people more knowledgeable than I.