Apples trees grown from seed actually do not match their parent - they are a genetic mix (just like us). What's more, they will most likely bear fruit that isn't pleasant to eat.
All the apple varieties you eat have been cultivated from a single original specimen, via cuttings or (more likely) grafting onto a convenient root stock.
Yes, essentially, if it hasn't otherwise been propagated. Also, the process for creating a new edible variety is fairly time and resource intensive, since it involves planting a lot of seeds and waiting a couple years to see if you get something worthwhile.
The story is also similar for rootstock. Apples are naturally a fairly large tree, which isn't convenient for harvesting. The rootstocks that apples are typically grafted onto are genetic variants that don't grow as large.
All the apple varieties you eat have been cultivated from a single original specimen, via cuttings or (more likely) grafting onto a convenient root stock.