Advice on "volunteer orchard"
I've been stuffing apples down gopher holes and letting apple starts grow for the last ~5 years once I realized this old Grandma apple tree was singing her death song. Now I've got clusters of young apple trunks all in over (And that's a nectarine on the right growing out of my old compost 😁. I was originally thinking I would learn to graft known varietals onto the sprouts since I know apples don't grow true to seed. But last summer/fall several of them made fruit which was actually pretty tasty. And I make cider, so I'll be able to use them.
Three questions - (1) which of the three young trees growing crowded in this first pic would you save? I was thinking the one on the left. (2) How should I prune it? Is it time to cut the central leader? It's about 10 ft (3m) high now. (3) Should I trim all these "apple patches" down to one tree now, or are there advantages to waiting (besides being able to taste which one is better)? I realize some of them are too close to each other (3b) how far apart should they be from each other?
(4) Anyone have suggestions for fun things to try with all these little trees?