Huge difference between the two. No way I would use the used vegetable oil in a 40k tractor or a 40k pickup. There are no standards to it, it's all done backyard, etc. There are no standards to it at all. It isn't regulated at all. You have to modify your vehicle, which will void warranties.
As far as shelf life it's guaranteed for six months. After that it's usually fine but you need to test it. But that's the same for diesel as well. With the B2 or B20 you treat it just the same as you would regular diesel. The extenders and pour points can be used the same as 100% diesel.