I don't think there is any way to know exactly which minute changes are made throughout the 9 - 48+ month lifecycle of a specific release. Mass-produced laptops are using sourced parts from many different companies...there could be products/components/parts from well over 100 companies inside a single MacBook Pro, and if Apple released all of the specifics and alterations, it would make people's heads explode. Further, if say 2, 3, 5, or more different companies are making the identical part, building it to Apple's spec, it would be extremely hard to individually document this (and it could give rise to people demanding a specific machine with or without a certain part from a certain maker, which would be a logistical nightmare, as was with the Samsung vs. LG screens.)
Apple could have conceivably made some minor alterations, as they aren't generally a company that remains complacent if they see an area where they can improve. For example, with the battery, they could switch to a slightly different electrolyte formulation that provides a slight bit more run time or better run time under heavier load. Or perhaps a minor change in the anodizing spec, for a more robust cosmetic finish that provides enhanced resistance to cosmetic damage. Or if they found that one of their parts suppliers was of acceptable quality but still inferior to other suppliers of the same part, they may have discontinued purchasing that part from that supplier. I don't think even most internal Apple sources would have the specifics on this for obvious reasons.
Nobody knows but Apple. Few years ago, they closely followed Intel's release cycle, bumping the specs every six months or so, but the Intel's cycle has since changed and things have slowed down in the industry considerably.
Agreed.
I've read that with the delays in the smaller die-shrinks, roadmaps and timelines ain't what they used to be!