The few registered cultivars from this cross always came from using caerulea as the pollen parent. Both P. edulis edulis (purple fruited) and P. edulis flavicarpa (yellow fruited) have been crossed with caerulea. Do you know which cultivar of edulis you have?

Both caerulea should cross with each other if they are different individuals (unique seedlings and not clones of the same individual).

Agrees.
Caerulea is not self fertile in my expierence, but if the 2 plants are grown from seeds, or clones of different parents your in luck.

Experiment. That's how we learn stuff.

Good luck-