I'll take a shot

1. Water cooled engine should be able to have tighter tolerances due to better cooling but that's a guess seems like aircooled engine would have more metal expansion and contraction due to an unregulated cooling system and would need more clearance
2. it doesn't, It doesn't
3. no part
4. skirt
5.I would guess as long as it takes to for the ring to shave of the high spots on the cylinder left from honing but then that would be the cylinder not the ring breaking in. I'll say the ring is harder since they break if not handle right and I've never seen the ring loose if it breaks and takes a ride on the cylinder wall
6. no parts
7. the cylinder

these are just guesses since I don't get paid to fix or build engines I'm not an expert so these are guesses
I would think if a engine goes sour early in it's life and it wasen't lean burned or run without oil
I would say it had a faulty part from the start be it rare these days with modern machine practices

So whats my score ?