I may be wrong, but I think the answer is yes.

Any time should be fine.

It is not a good idea to add anything high in carbon the same day as you put in plants. I think I would use this as a mulch and would not mix it into the soil until after the plants are done growing, if then.

I may be wrong, but I think the answer is yes.

Although not really a yes or no question, I love it!! The second part of bpgreen's answer is a bit more on point and perfectly correct - you can add it at any time. We have actually done testings of planting tomatoes directly in a bag of Bumper Crop and a similar product called Harvest Supreme and the results were quite spectacular. It is entirely organic with a good nutrient blend and if you so desired, you could fill your entire raised bed with it. Go for it!