That depends how religious you are. Orthodox Jews NEVER buy anything non-kosher.

Yes, kosher wine can be stored in the same place as non-kosher wine as they're in sealed bottles.

If you mean truffles infused with wine, it would be kosher if the wine is kosher (and the processing pots or vessels had not previously handled non-kosher foods).

The wine has to have kosher symbols and rabbinical supervision.

Anyone can become an alcoholic whether wine is kosher or not.

Kosher wine or kosher grape juice