>>2574666>>2574669The more the merrier with OP breeding. Diversity over quantity, you can get some wild stuff! Get some welded wire sheets and make a shield when they go outside, I don't know if rabbits ring-bark plants but you should probably protect. Go all out on your potting soil too, trees really appreciate investment in the soil as they usually sit in the same pot for years
Cross pollination is a crapshoot with apples, there are pollination charts for named cultivars, but OP seed can be completely random, if your neighbors have apples though the bees will do that job for you.
>pic related