1) Yes, it is okay to use zero. If you don't know the basis, you must use zero.
2) Yes, it is based on the sales price. 1099-B is already giving you that when they tell you the proceeds. You don't have to calculate anything,
3) No, as stated, TurboTax no longer does that. You could look back at brokers' statements as indicated. Again, if you have no information whatsoever, use zero.
