Does apple seeds germinate inside an apple?
I think not.
First an apple has to break down and spend a winter or better be eaten by some animal and spread by natural dissemination elsewhere in the droppings of the animal, where it will be naturally stratified with a passing cold season and will germinate next Spring.
If seeds were to sprout inside an apple, the cotyledons (the first false leaves that develops when the sprout unfolds itself) would not be able to reach the light going through it's casing and the thick somewhat hard pulp and the growth process would be chocked. Also, another scenario would be that if the seeds in the apples fallen under a tree were to germinate as such, there soon would be a thick cluster of apple trees of all sizes under the parent tree competing for space. Nature is a lot smarter.
Just a personal view.
But since the question has been brought up, I have seen a case of germination in a fruit and I will tell you about it.
I had a variety of tomato called Longkeeper, that were meant to be picked green and slowly turn orange over the winter. The taste was not fantastic but it meant fresh tomatoes in the winter. Those tomatoes sure were good keepers. Once I cut a fresh tomato in March (picked in September) and found that the seeds had germinated inside the plant. I though this too weird and I queried about the Longkeeper. I discovered that it was genetically modified!!?!
Developpers had implanted a gene of scorpio in the genetic makeup of the tomato for longkeeping.
I am now back to canned tomatoes.
Just another personal view.