The major versions (and minors) are thoroughly documented in API diffs, the IDE suggests what to modify according to your platform target.
The review guidelines are basically changing for the major versions, accordingly to the new tech introduced, and most of them are dictated by common sense. If something goes awry the review team is available to discuss with you. Good luck getting an Android app reinstated if it is taken down.
The certificates are a pain in the ass, no way around that, but the rest of the platform makes up for this, the tools and language(s) are way easier to use.